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    An Assessment of the Paper Industry Firms Listed in Borsa Istanbul Using Entropy-Based MAUT Method
    (Springer International Publishing Ag, 2017) Apan, Mehmet; Oztel, Ahmet; Islamoglu, Mehmet
    The aim of this study is to measure the market and financial performance of the paper industry firms listed in Borsa Istanbul by adopting multiple attribute utility theory (MAUT) which is one of the most widely used multi-criterion decision-making (MCDM) methods. The performance of the firms is assessed for the period between 2011 and 2013. The weights of evaluation criteria are determined by applying entropy, which is an objective weighting method. In the analysis, the firms are ranked by integrating entropy-based MAUT method. According to the analysis results, Kartonsan has the highest performance rate for all the years, whereas Viking has shown the poorest performance except for the year 2011. During the period, Mondi and Olmuksan, which are acquired by foreign investors, have shown relatively stable performance; however, the performance rate of Kaplamin is unstable. The only firm that has a rising performance trend during the period is Alkim. On the other hand, the sample is also analyzed by using equal weighted MAUT.
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    Comparative Empirical Analysis of Financial Failures of Enterprises with Altman Z-Score and VIKOR Methods: BIST Food Sector Application
    (Univ Wollongong, 2018) Apan, Mehmet; Oztel, Ahmet; Islamoglu, Mehmet
    This study includes an empirical review of the financial failure of enterprises. For the empirical analysis, 2008-2014 period data for enterprises operating in the Food and Drink Sector traded on BIST (Borsa Istanbul), were used. The financial failures of these enterprises were first determined according to the Altman Z-Score method, and the financial success rankings of the enterprises were then determined by the VIKOR (VIseKriterijumsa Optimizacija I Kompromisno Resenje) method, which is one of the MCDM (Multiple Criteria Decision-Making) methods. The empirical analysis results obtained from these two different methods have been comparatively evaluated and interpreted. In this study, the VIKOR method is suggested as an alternative method for financial failure analysis.
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    Determination of the Efficiencies of Textile Firms Listed in Borsa Istanbul by Using DEA-Window Analysis
    (Sosyoekonomi Soc, 2019) Apan, Mehmet; Alp, Ihsan; Oztel, Ahmet
    Global competition enables countries' advantageous sectors to stand out as an indicator of their economic power. The importance of these sectors may vary by country or the time period they operate in. The textile industry is one of the sectors that significantly contributes to Turkey's economic growth. Thus, it is important to monitor the financial activities of the firms in the textile sector as a performance indicator since it is evident that the financial efficiency of each company will contribute positively to the overall efficiency of the whole sector. In this study, the financial activities of 19 firms in the textile sector being traded on Borsa Istanbul (BIST) for the period 2008-2017 are examined. For efficiency analysis, DEA (Data Envelopment Analysis)-Window Analysis method was applied by using financial indicators of these companies. It was observed that the highest average efficiency value of the companies was realized in 2017 with 94.09%. The average activity levels in other years were found to be in the range of 60%-90%. In the empirical analysis, the efficiency values of the top five companies were determined to be at the level of 90%-100%. DESA has achieved the most successful performance in average efficiencies with a score of 98.04 when the whole period is considered. SONMEZ and MENDERES firms have taken the second and the third places with scores of 97.40 and 94.74, respectively. The close performances of the top three firms were also observed in three-years windows. However, in the three-year window analysis, SONMEZ ranked the first, DESA ranked the second and MENDERES ranked the third according to their average scores. One of the reasons for this small difference between the rankings is that, firstly, the firms' performances have been very close to each other, and secondly the effect of the low score (76.11) obtained by SONMEZ in 2008 has been diminished for the firm in the three-year window analysis. KARSU occupied the last place with the lowest average efficiency score in both rankings.
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    Thermoplastic composites of polypropylene/biopolymer blends and wood flour: Parameter optimization with fuzzy-grey relational analysis
    (Sage Publications Ltd, 2022) Kelleci, Orhan; Aydemir, Deniz; Altuntas, Ertugrul; Oztel, Ahmet; Kurt, Rifat; Yorur, Huseyin; Istek, Abdullah
    In this study, blends of polypropylene (PP) with polylactic acid (PLA) and polyhydroxybutyrate (PHB) biopolymers and wood flour were prepared, and Fuzzy and Grey Multi-Criteria Decision-Making (MCDM) methods were used to determine the blends with the best properties. The physical, mechanical, thermal, structural, and morphological properties of the composites were determined. The obtained results showed that PLA and wood flour generally improved the mechanical properties of the PP composites. However, wood flour did not exhibit a homogeneous distribution in the matrix. The density of the composites generally increased with the addition of both PLA and PHB. X-ray diffraction analysis showed that the crystallinity index of the composites generally decreased due to the low crystallinity of biopolymers. Thermal stability did not change with the addition of PLA and PHB, but the addition of wood increased thermal stability. According to the MCDM analysis, both Fuzzy and Grey results were similar.
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    Wood Flour-Reinforced Green Composites: Parameter Optimization via Multi-criteria Decision-Making Methods
    (Springer, 2022) Kelleci, Orhan; Aydemir, Deniz; Altuntas, Ertugrul; Kurt, Rifat; Oztel, Ahmet; Yorur, Huseyin; Istek, Abdullah
    The aim of this study was to investigate the physical, mechanical, morphological, structural, and thermal properties of polylactic acid (PLA) and polyhydroxybutyrate (PHB) biopolymer composites reinforced with thermally treated wood flour and to determine the formulations having optimum properties by using multi-criteria decision-making (MCDM) methods. As a filler, Scots pine wood flour (untreated and thermally treated at 212 degrees C) was used at the loading rates of 10% and 30%. The samples were prepared using a twin-screw extruder and then by compression molding. The results showed that the addition of both thermally treated and untreated wood flour slightly increased the density of the composites. According to the color measurement, the thermally treated wood composites were slightly darkened in appearance. In the composites, with both wood fillers, the water absorption and thickness swelling ratios had increased during the 20-250 days of water exposure. Lower water absorption and thickness swelling rates were found for the composites with thermally treated wood filler compared to the other composites. The wood fillers generally lowered the mechanical properties of the PLA and PLA/PHB composites, with the PHB composites as the exception. However, the tensile modulus and Izod impact strength of the composites generally increased with the addition of wood fillers. Morphological examination performed by scanning electron microscopy (SEM) indicated that the wood flour was mostly homogeneously distributed in the matrix, which improved the mechanical properties of the composites. Thermogravimetric analysis (TGA) showed that the addition of wood filler to the neat biopolymers as a rule did not provide significant improvement in the thermal stability; however, the fillers increased the thermal stability of neat PHB. The Fourier-transform infrared (FTIR) spectroscopy detected no differences in the chemical structure of the composites. The X-ray diffraction (XRD) results indicated a general increase in the crystallinity with the addition of wood fillers to the neat biopolymers and the blends. All the findings were subjected to MCDM analysis to determine the formulation having the optimum properties and the results showed this to be the neat PLA sample.