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RISS 인기검색어
- 검색키워드
- 저자 : Karel Svoboda (검색결과 4 건)
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Effect of Initial Melting Temperature on Crystallization of Polypropylene/Organoclay Nanocomposites
Petr Svoboda,Krunal Trivedi,Dagmar Svobodova,Pavel Mokrejs,Karel Kolomaznik 한국고분자학회 2012 Macromolecular Research Vol.20 No.7
Polypropylene (PP) nanocomposites were prepared by melt intercalation using an intermeshing co-rotating twin-screw extruder. The influence of organoclay (Cloisite 20A) and maleic anhydride modified polypropylene (PPMA)on various properties was explored. The effect of the initial melting temperature on crystallization kinetics was investigated by differential scanning calorimetry (DSC) and optical microscopy. DSC has revealed a gradual decrease in crystallization kinetics with an increase in initial melting temperature for two-component systems (PP/PP-MA and PP/20A). However, in the case of a three-component system (PP/PP-MA/20A), the decrease of crystallization kinetics in the range of initial melting temperature being 200-240 oC was followed by an increase in the temperature range 240-260 oC. After initial melting at 250 oC, many spherulites were discovered in the three-component system. This unusual crystallization behavior was explained with the help of Fourier transform infrared spectroscopy (FTIR),where an increase in the Si-O peak with the increasing initial melting temperature was detected, which indicates the presence of large surface of clay layers. The morphology of nanocomposites was also investigated by transmission electron microscopy (TEM). The X-ray diffraction (XRD) analysis has revealed a decrease in the peak intensity with an increase in initial melting temperature, which suggests exfoliation caused by fast diffusion at high temperatures.
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Biomass gasification in internal circulating fluidized beds: a thermodynamic predictive tool
Francesco Miccio,Karel Svoboda,Jean-Pierre Schosger,David Baxter 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.4
The paper deals with a high efficiency process for biomass gasification based on the concept of the internal circulating fluidized bed (ICFB). A modeling tool has been developed for the prediction of theoretical values for the main species in a syngas produced by ICFB gasification. A thermodynamic sub-model has been utilized and integrated with a simplified lumped model of the gasifier. The model predicts H2 concentration up to 61% on water free basis. The comparison with calculations for one stage gasification demonstrates ICFB process is preferable, no dilution with inert gas occurring. Among the studied variables, the steam/fuel ratio and the fuel moisture exert the largest influence on the hydrogen yield with percentage changes up to 15% in the explored range of the variables.
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Trtilek, Radek,Havlova, Vaclava,Podlaha, Josef,Svoboda, Karel,Otcovsky, Tomas Korean Radioactive Waste Society 2021 방사성폐기물학회지 Vol.19 No.1
The article summarises the status and competence of UJV Rez, a. s. (up to 2012, the Nuclear Research Institute Rez, Czech Republic) in the field of radioactive waste (RAW) management as a company managing of 95% of institutional radioactive wastes in Czech Republic. UJV Rez a. s. has been one of the Czech Republic's key research and engineering institutions in the field of nuclear energy production since 1955. The company processes and conditions prior to storage 95% of so-called institutional RAW and is the principal partner of the state with respect to the research support of the Czech deep geological repository development project. UJV Rez a. s. boasts its own accredited radiochemical analytical test laboratory, unique of its kind in the Czech Republic. Of equal importance is UJV Rez's active participation in a range of international organisations and associations and its involvement in wide range of international projects, and so as European projects. One of them is EU funded project PREDIS: Pre-disposal management of radioactive wastes, that has started at September 2020, focused on the field of low level radioactive waste (LLW) and intermediate level radioactive waste (ILW) pre-disposal.
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Slow-rate devolatilization of municipal sewage sludge and texture of residual solids
Miloslav Hartman,Bohumír Čech,Michael Pohořelý,Karel Svoboda,Michal Šyc 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.10
Ash-rich sludge samples originating in four large plants were analyzed and employed to explore primarily the kinetics and the chemistry of devolatilization. A gravimetric, slowly increasing-temperature method was used in the range 298-1,123 K in a milieu of nitrogen. As an intricate combination of numerous (bio)organic and inorganic compounds, the dry sludge commences devolatilizing at approximately 418 K. The bulk of organic matter is released up to 823 K, at the rate becoming very slow thereafter. Basic constituents of the product gas are CO2, CO, H2, and CH4 with undesired nitrogenous, sulfurous, and chloro compounds. The residual solids contain significant amounts of organic matter/carbon and, on account of their favorable textural characteristics, they can be viewed as promising sorbents or catalysts. Kinetic triad was inferred from the experimental data: the model is well-capable of simulating the process of devolatilization and can be used for design considerations. An explicit equation, based upon a tractable approximation to the temperature integral (for [E/(RT)]0.1), has been verified and proposed for predicting the maximum reaction rate temperature. Remarkable differences in thermal behavior were explored in detail between the sludge and the alkali bicarbonates.
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