Türkiye deki Gayrimenkul Yatırım Ortaklıkları (GYO) Piyasasının Kurumsal Finans Teorileri Kapsamındaki Analizi: Arbitraj Fiyatlama Modeli ve Vergi Arbitrajı için Olay Çalışması Uygulamaları

TÜBİTAK SOBAG Proje01.11.201

Optimizing of Wear Performance on Elevated Temperature of ZrO2 Reinforced AMCs Using Weighted Superposition Attraction Algorithm

462-474In the current study, the zirconium oxide (ZrO2) reinforced Aluminium Matrix Composites (AMCs) was designed as a brake lining and produced by mechanical alloying (MA) method. Wear tests of AMCs were performed according to ASTM G-99 at different sliding distance, operating temperatures and load in the range of 53 to 94 m, 20 to 340℃ and 10 to 30 Nrespectively. Optimum wear performance parameters were determined using the Weighted Superposition Attraction (WSA)algorithm. Firstly, to formulize the problem as an optimization problem through the guidance of the regression modelling, anexperimental design has been constructed, and the wear tests have been done at different reinforced rates, operatingtemperature and loads. Secondly, WSA algorithm has been adapted to tackle the formulated optimization problem.According to the results of WSA algorithm, the optimum rate of zirkonium oxide (ZrO2), load and operating temperaturewas determined as 12%, 206.33°C and 21.20 N respectively while keeping the friction coefficient between 0.15–0.24

What Determines REIT Returns in Turkey? An Application of Time-Varying Arbitrage Pricing Model in an Emerging REIT Market

This paper investigates the macroeconomic sources of time-varying risk premia in Turkish REIT industry within the arbitrage pricing theory framework Turkish REIT industry differs substantially from the global REIT market as Turkish REITs do not have to pay out dividends, yet enjoy the exemption from paying corporate taxes, and have highly concentrated ownership structure. These fundamental differences have significant impacts on the performance of REITs compared to other stocks listed on Borsa Istanbul (BIST), especially in terms of the inflation-hedging characteristics and time-varying systematic risk behaviour. This article evaluates the Turkish REIT industry by using a time-varying multifactor model, which compares the REIT industry excess returns with various macroeconomic factors, including GDP growth, industrial production growth, inflation risk premium, and stock market risk premium. Our results provide the evidence of time-varying linkages among macroeconomic risks and the conditional first and second moments of excess returns on REITs. We find that among the macroeconomic factors, inflation risk appears to be the major concern in REIT investment. Additionally, Turkish REITs behave more like stocks than real estate. The documented perverse inflation hedges of REITs, the positive correlation between REIT returns and volatility of real economic activity, and the significant influence of ISE equity risk premium on REIT returns can be quoted as the indications of deviation of REITs' performance from real estate performance. If REITs behave more like stocks than real estate, the diversification benefits of having REITs in a multi-asset portfolio is seriously reduced.Publisher's Versio

Experimental investigation of the effect of antioxidant additives on NOx emissions of a diesel engine using biodiesel

WOS: 000333402900006In this study, the effect of the antioxidant additives on the oxidation stability of biodiesel and the exhaust emissions of a diesel engine has been studied. Biodiesel used in this study was produced via transesterification process from canola oil, and was blended with diesel fuel 20% by volume (B20). Antioxidant additives butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tert-butylhydroquinone (TBHQ) and 2-ethylhexyl nitrate (EHN) were individually dissolved at concentrations of 0, 500, 750 and 1000 ppm by weight in B20 fuel blend for experiments. The test results of oxidation stability showed that the effectiveness of the antioxidants was in the order of TBHQ > BHA > BHT > EHN. According to exhaust emissions test results, antioxidant additives had quite effects on oxides of nitrogen (NOx), carbon monoxide (CO) and hydrocarbon (HC) emissions of diesel engine running on biodiesel. A 1000 ppm concentration of EHN additive was optimal as NOx levels were substantially reduced in the whole engine speed in comparison with B20 fuel. (C) 2014 Elsevier Ltd. All rights reserved.Ege UniversityEge University [08-GEE-017]This study was conducted at Solar Energy Institute of Ege University, and was supported by the scientific research project of Ege University (08-GEE-017)

Effects of antioxidant additives on engine performance and exhaust emissions of a diesel engine fueled with canola oil methyl ester-diesel blend

WOS: 000327576800017An experimental investigation has been carried out to analyze the effect of antioxidants on engine performance and exhaust emissions of a diesel engine fueled with B20 (20 vol.% canola oil methyl ester and 80 vol.% diesel fuel blend). The four synthetic antioxidants, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tert-butylhydroquinone (TBHQ) and 2-ethylhexyl nitrate (El-IN), were tested on a Land Rover turbocharged direct injection (TDI) 110 type diesel engine with water cooled, 4-cycl and 4-cylinder. The addition of antioxidants to B20 did not cause any negative effect on basic fuel properties of B20. According to engine performance test results, brake specific fuel consumption (BSFC) of B20 with antioxidants decreased compared to those of B20 without antioxidants. A 1000 ppm concentration of TBHQ was optimal as BSFC values were considerably reduced (10.19%) in the whole engine speeds when compared to B20. EHN antioxidant with B20 presented the best mean oxides of nitrogen (NOx) with a reduction of 4.63%. However, formation of carbon monoxide (CO) emissions has been increased with addition of each of the antioxidants to B20. (C) 2013 Elsevier Ltd. All rights reserved.scientific research project of Ege UniversityEge University [08-GEE-017]This work was conducted at Solar Energy Institute of Ege University, and was financially supported by the scientific research project of Ege University (Project Number: 08-GEE-017). The authors wish to thank people who were involved in this study

Optimizing cetane improver concentration in biodiesel-diesel blend via grey wolf optimizer algorithm

Biodiesel and their blends with diesel have long been used as alternative fuels in diesel engines. In particular, B20 is recommended in most studies since it reduces the exhaust emissions and provides satisfactory engine torque close to diesel fuel. On the other hand, low cetane number of biodiesel leads to higher oxides of nitrogene (NOx) emission when compared to those of the diesel fuel. Formation of NOx emissions has a strong correlation with cetane number of fuels, which increases with the reduction of the cetane number. The current paper focuses on finding the optimum 2-ethylhexyl nitrate (EHN) (cetane improver) concentration and the engine speed for 20 vol% canola oil methyl ester and 80 vol% diesel fuel blend (B20). For that reason, experimental design is created and the experiments have been done on TDI diesel engine at full load and different engine speed conditions to be able to model the problem as an optimization problem by means of the regression modelling. Accordingly, the developed model in consequence of the test results of the engine is optimized via the grey wolf optimizer (GWO) algorithm taking into account of engine performance and emission parameters viz. brake torque, brake power, brake specific fuel consumption (BSFC), brake thermal efficiency (BTE), NOx, and carbon dioxide (CO2), to identify the rate of concentration of EHN in B20 and engine speed. Finally, confirmation tests were employed to compare the output values of the concentration that were identified through the GWO algorithm, and further statistical analyses indicate the consistency between the real experimental results and the results obtained through the GWO algorithm. The optimum EHN concentration and engine speed was determined as 743 mg/L and 3221 rpm respectively. Test results of engine performance indicated that brake power and BSFC of optimum blend at 3221 rpm decreased while brake torque and BTE increased in comparison with those of B20 without EHN. CO2 and NOx exhaust emissions decreased as 11.19% and 4.63% respectively

Optimizing of Wear Performance on Elevated Temperature of ZrO2 Reinforced AMCs Using Weighted Superposition Attraction Algorithm

In the current study, the zirconium oxide (ZrO2) reinforced Aluminium Matrix Composites (AMCs) was designed as a brake lining and produced by mechanical alloying (MA) method. Wear tests of AMCs were performed according to ASTM G-99 at different sliding distance, operating temperatures and load in the range of 53 to 94 m, 20 to 340℃ and 10 to 30 N respectively. Optimum wear performance parameters were determined using the Weighted Superposition Attraction (WSA) algorithm. Firstly, to formulize the problem as an optimization problem through the guidance of the regression modelling, an experimental design has been constructed, and the wear tests have been done at different reinforced rates, operating temperature and loads. Secondly, WSA algorithm has been adapted to tackle the formulated optimization problem. According to the results of WSA algorithm, the optimum rate of zirkonium oxide (ZrO2), load and operating temperature was determined as 12%, 206.33°C and 21.20 N respectively while keeping the friction coefficient between 0.15–0.24