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Aleksandra Rutkowska

Abstract

Portfolio optimization, one of the most rapidly growing field of modern finance, is selection process, by which investor chooses the proportion of different securities and other assets to held. This paper studies the influence of membership function’s shape on the result of fuzzy portfolio optimization and focused on portfolio selection problem based on credibility measure. Four different shapes of the membership function are examined in the context of the most popular optimization problems: mean-variance, mean-semivariance, entropy minimization, value-at-risk minimization. The analysis takes into account both: the study of necessary and sufficient conditions for the existence of extremes, as well as the statistical inference about the differences based on simulation.

Open access

Łukasz Okruszek, Aleksandra Rutkowska and Joanna Wilińska

Differences in semantic clustering and switching were examined in men with frontal lobe lesions, men with schizophrenia and healthy men. Men with frontal lobe lesions and men with schizophrenia generated fewer words than healthy men and presented intact clustering, but decreased switching during the semantic fluency task. However, after controlling for the number of words produced, between-group differences in switching disappeared. These findings suggest that all three groups used similar strategies of clustering and switching during the semantic fluency task, although men with frontal lobe lesions and men with schizophrenia did it less efficiently than healthy men.

Open access

Patrycja Wojciechowska, Aleksandra Heimowska, Zenon Foltynowicz and Maria Rutkowska

Degradability of organic-inorganic cellulose acetate butyrate hybrids in sea water

Environmental degradability of novel organic-inorganic cellulose acetate butyrate hybrids obtained via solgel process was investigated. The degradation of hybrids was studied under marine exposure conditions in the Baltic Sea for a period of 25 weeks. The influence of characteristic parameters of sea water on the degree of degradation monitored by changes of weight and optical microscopy was discussed. The degraded samples were also examined by FT-IR spectroscopy. It has been established that the CAB/silica hybrids are more susceptible to biodegradation in sea water environment than pure cellulose acetate butyrate.