Browsing by Author "Maryška, Jiří"
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- ItemA Review on Membrane Technology and Chemical Surface Modification for the Oily Wastewater Treatment(MDPI, 2020-03-11) Yalcinkaya, Fatma; Boyraz, Evren; Maryška, Jiří; Kučerová, KláraCleaning of wastewater for the environment is an emerging issue for the living organism. The separation of oily wastewater, especially emulsified mixtures, is quite challenged due to a large amount of wastewater produced in daily life. In this review, the membrane technology for oily wastewater treatment is presented. In the first part, the global membrane market, the oil spill accidents and their results are discussed. In the second and third parts, the source of oily wastewater and conventional treatment methods are represented. Among all methods, membrane technology is considered the most efficient method in terms of high separation performance and easy to operation process. In the fourth part, we provide an overview of membrane technology, fouling problem, and how to improve the self-cleaning surface using functional groups for effectively treating oily wastewater. The recent development of surface-modified membranes for oily wastewater separation is investigated. It is believed that this review will promote understanding of membrane technology and the development of surface modification strategies for anti-fouling membranes.
- ItemDual variable methods for mixed-hybrid finite element approximation of the potential fluid flow problem in porous media(Technická Univerzita v Liberci, 2006) Arioli, M.; Maryška, Jiří; Rozložník, Miroslav; Tůma, MiroslavMixed-hybrid finite element discretization of Darcy's law and the continuity equation that describe the potential fluid flow problem in porous media leads to symmetric indefinite saddle-point problems. In this paper we consider solution techniques based on the computation of a null-space basis of the whole or of a part of the left lower off-diagonal block in the system matrix and on the subsequent iterative solution of a projected system. This approach is mainly motivated by the need to solve a sequence of such systems with the same mesh but different material properties. A fundamental cycle null-space basis of the whole off-diagonal block is constructed using the spanning tree of an associated graph. It is shown that such a basis may be theoretically rather ill-conditioned. Alternatively, the orthogonal null-space basis of the sub-block used to enforce continuity over faces can be easily constructed. In the former case, the resulting projected system is symmetric positive definite and so the conjugate gradient method can be applied. The projected system in the latter case remains indefinite and the preconditioned minimal residual method (or the smoothed conjugate gradient method) should be used. The theoretical rate of convergence for both algorithms is discussed and their efficiency is compared in numerical experiments. Copyright © 2006, Kent State University.
- ItemSpektrální analýza diskretizovaného modelu piezoelektrického rezonátoru(Technická Univerzita v Liberci, 2006) Rálek, Petr; Maryška, Jiří
- ItemSurface-modified nanofibrous PVDF membranes for liquid separation technology(2019) Boyraz, Evren; Yalcinkaya, Fatma; Hrůza, Jakub; Maryška, JiříPreparing easily scaledup, cost-effective, andrecyclablemembranes for separation technology is challenging. In the present study, a unique and newtype ofmodified polyvinylidene fluoride (PVDF) nanofibrous membrane was prepared for the separation of oil-water emulsions. Surface modification was done in two steps. In the first step, dehydrofluorination of PVDF membranes was done using an alkaline solution. After the first step, oil removal and permeability of themembraneswere dramatically improved. In the second step, TiO2 nanoparticles were grafted onto the surface of the membranes. After adding TiO2 nanoparticles, membranes exhibited outstanding anti-fouling and self-cleaning performance. The as-prepared membranes can be of great use in new green separation technology and have great potential to deal with the separation of oil-water emulsions in the near future.