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Key Drivers of Volatility in BISTt100 Firms Using Machine Learning Segmentation
No full textThis study conducts a comprehensive volatility analysis among firms listed on the BIST100 index using machine learning techniques and panel regression models. Focusing on the period from 2006 to 2023, the study excludes financial firms, resulting in a dataset of 46 companies. The methodology follows a two-step process: First, firms are clustered into low and high-volatility groups using Principal Component Analysis (PCA) and the K-means algorithm; second, panel regression models are applied to determine the financial ratios influencing stock price volatility. The Parkinson Volatility measure is used as the dependent variable, while independent variables include Return on Assets (ROA), Return on Equity (ROE), liquidity ratios, firm beta, and leverage ratios. Results indicate that firm beta has a statistically significant positive impact on volatility across all models, while the current ratio negatively affects volatility in the model 1. These findings provide valuable insights for investors and policymakers regarding risk management in the Turkish stock market. Applying machine learning and advanced econometric techniques adds to the literature on volatility forecasting and financial decision-making. © 2025 Elsevier B.V., All rights reserved
Hybridization of Debohid With Enn Algorithm for Highly Imbalanced Datasets
No full textMachine learning algorithms assume that datasets are balanced, but most of the datasets in the real world are imbalanced. Class imbalance is a major challenge in machine learning and data mining. Oversampling and undersampling methods are commonly used to address this issue. Edited Nearest Neighbor (ENN) and Synthetic Minority Oversampling Technique (SMOTE) are essential methods for undersampling and oversampling, respectively. DEBOHID is a recently proposed differential evolution-based oversampling approach for highly imbalanced datasets. In this work, DEBOHID and ENN methods are combined to present a novel hybrid method called D-ENN. The performance of D-ENN was evaluated using 44 highly imbalanced datasets. A parameter analysis was conducted on D-ENN to determine the optimal values for the F, CR and D-ENN-Type parameters. Three classifiers were used in the study: Support Vector Machines (SVM), Decision Tree (DT), and K-nearest Neighbor (kNN), and reported their G-mean and Area Under Curve (AUC) values. Upon evaluation of the average Winner, Mean Rank and Final Rank values obtained for each classifier and metric pair, the proposed D-ENN method demonstrated superior performance compared to nine state-of-the-art sampling methods, with an average Winner value of 13, an average Mean Rank value of 3.40 and an average Final Rank value of 1
Analyzing the Impact of the 2023 General Elections on Land Prices Using Machine Learning: a Case Study in Çanakkale, Turkey
No full textThis study analyses the impact of the general elections to be held on 14 May 2023 on the real estate market in Turkey. The aim of the study is to develop a model to predict land unit prices (₺/m²) by analysing land prices, exchange rates and gold values observed before (February-March-April) and after (May-June-July) elections for Ayvacık, Bayramiç, Biga, Çan, Eceabat, Ezine, Gelibolu, Lapseki, Merkez and Yenice districts of Çanakkale province. Daily fluctuations in foreign exchange and gold values, which are the main economic parameters in the study, were recorded during the election period. The findings of this research, which predicts price movements in the property market using machine learning methods such as regression trees, reveal that unit prices of land generally tend to increase with increases in exchange rates, but in some districts where gold prices increase, the unit price shows a reverse trend. This is attributed to the fact that investors prefer gold as a safer asset in times of economic uncertainty. The results obtained can help investors and buyers to predict future trends in property prices, as well as contribute to the development of economic policies by experts to stabilise fluctuations in investment instruments
The Effect of Radiation Damage on the Light Yield and Uniformity of Candidate Plastic Scintillator Tiles for the Cms Hadron Calorimeter Upgrade
No full textPasztor, Gabriella/0000-0003-0707-9762; Klyukhin, Vyacheslav/0000-0002-8577-6531; Madrid, Christopher/0000-0003-3301-2246; Papageorgakis, Christos/0000-0003-4548-0346; Vilela Pereira, Antonio/0000-0003-3177-4626; Bodek, Arie/0000-0003-0409-0341; Belyaev, Andrey/0000-0003-1692-1173; Lokos, Sandor/0000-0002-4447-4836; Tiras, Emrah/0000-0002-5628-7464; Mora Herrera, Maria Clemencia/0000-0003-3915-3170; Tok, Ufuk Guney/0000-0002-3039-021X; Hatakeyama, Kenichi/0000-0002-6012-2451; Saygin, Kadir/0000-0002-8419-1400; Dubinin, Mikhail/0000-0002-7766-7175; Flaecher, Henning/0000-0002-5371-941X; Dolek, Furkan/0000-0001-7092-5517; Sen, Sercan/0000-0001-7325-1087; Belloni, Alberto/0000-0002-1727-656X; Kiminsu, Ugur/0000-0001-6940-7800; Levchuk, Leonid/0000-0001-5889-7410; Demiroglu, Zuhal Seyma/0000-0001-7977-7127; Gandrajula, Reddy Pratap/0000-0001-9053-3182; Seidel, Markus/0000-0003-3550-6151; Csanad, Mate/0000-0002-3154-6925; Kaur, Amandeep/0000-0002-1640-9180; Zorbakir, Ibrahim Soner/0000-0002-5962-2221; Kolberg, Ted/0000-0002-0211-6109; Alves, Gilvan/0000-0002-8369-1446; Kanuganti, Ankush Reddy/0000-0002-0789-1200; Lawhorn, Jay/0000-0002-8597-9259; Lee, Sung-Won/0000-0002-3388-8339; Polikarpov, Sergey/0000-0001-6839-928X; Tully, Christopher/0000-0001-6771-2174; Landsberg, Greg/0000-0002-4184-9380; Lai, Yihui/0000-0002-7795-8693A study has been performed to understand the effects of radiation damage on various plastic scintillator tiles considered for a possible upgrade of the hadron calorimeter of the CMS detector. Measurements were made with unirradiated tiles and with tiles that had been irradiated in the CMS collision hall to a dose of 44 kGy. Results are presented for the tiles of different shapes in terms of the energy spectrum, efficiency as a function of the position at which each tile was hit, as well as light yield. All the tiles showed a light reduction of up to about 50%. The tiles with the shape currently used in the CMS detector did not see increased non-uniformity of light collection, while a significant disuniformity was observed for the tiles considered as alternatives.The authors would like to thank CERN for the operations of the SPS accelerator; Dragoslav Lazic for supporting operations in the H2 test-beam area; Chuck Hurlbut (Eljen Technology) for the advice on scintillators, and the preparation of test samples; Janina Gielata (FNAL) for the preparation of optical connections. Individuals have received support from the Belgian Fonds de la Recherche Scientifique, and Fonds voorWetenschappel.k Onderzoek; the Brazilian Funding Agencies (CNPq, CAPES, FAPERJ, FAPERGS, and FAPESP); SRNSF (Georgia); the Bundesministerium fur Bildung und Forschung, the Deutsche Forschungsgemeinschaft (DFG), under Germany's Excellence Strategy -EXC 2121 "Quantum Universe" -390833306, and under project number 400140256 -GRK2497, and Helmholtz-Gemeinschaft Deutscher Forschungszentren, Germany; the National Research, Development and Innovation Office (NKFIH) (Hungary) under project numbers K 128713, K 143460, and TKP2021-NKTA-64; the Department of Atomic Energy and the Department of Science and Technology, India; the Ministry of Science, ICT and Future Planning, and National Research Foundation (NRF), Republic of Korea; the Lithuanian Academy of Sciences; the Scientific and Technical Research Council of Turkey, and Turkish Energy, Nuclear and Mineral Research Agency; the National Academy of Sciences of Ukraine; the US Department of Energy.Belgian Fonds de la Recherche Scientifique; Fonds voorWetenschappel.k Onderzoek; CAPES; FAPERJ; FAPERGS; FAPESP; SRNSF (Georgia); Bundesministerium fur Bildung und Forschung; Deutsche Forschungsgemeinschaft (DFG) [EXC 2121, 390833306, 400140256 -GRK2497]; Helmholtz-Gemeinschaft Deutscher Forschungszentren, Germany; National Research, Development and Innovation Office (NKFIH) (Hungary) [K 128713, K 143460, TKP2021-NKTA-64]; Department of Atomic Energy; Department of Science and Technology, India; Ministry of Science, ICT and Future Planning, and National Research Foundation (NRF), Republic of Korea; Lithuanian Academy of Sciences; the Scientific and Technical Research Council of Turkey, and Turkish Energy, Nuclear and Mineral Research Agency; National Academy of Sciences of Ukraine; US Department of Energ
Pll Kontrollü İki Fazlı Yürüyen Dalga İndüksiyon Isıtıcı Tasarımı
No full textInduction heating is a fast, non-contact, clean, efficient, easy and precisely controllable heating technology. Due to these features, it is frequently preferred in industrial applications such as surface hardening, tempering, annealing, curing; in some medical applications and in domestic applications such as induction furnaces. In induction heating systems, the resonance frequency of the system changes and efficiency decreases due to the changing parameters of the workpiece depending on the temperature. In this thesis, keeping the induction heating system constantly at resonance has been achieved by using phase locked loop (PLL). Induction coil has been made of litz wire to reduce the skin effect. The problem of insufficient heat increase in the middle parts of the workpiece encountered in transverse flux induction heating systems has been solved by the two-phase traveling wave induction heater design. Ferrite magnetic flux concentrator has been used to reduce stray magnetic fields and direct the magnetic flux directly to the workpiece. Numerical analyses have been performed using the COMSOL Multiphysics program using the finite element method on 3D models. In the relevant program, a comparison of single and double coil transverse flux induction heating models with and without concentrators have been made. From the numerical analysis results, it has been observed that using traveling wave induction heating and magnetic flux concentrator for homogeneous heating on the workpiece surface in transverse flux induction heating systems increased the performance of the system. The system performance has been evaluated by measuring the temperature created on the workpiece by the induction heating system with a thermal camera. Thermal analyses have been performed using the Fluke Smartview program. The minimum, maximum, average values and standard deviations of the temperature values occurring on the workpiece surface, and temperature changes along the two horizontal axes have been examined. In addition, the time it took for a selected point to reach a certain temperature has been evaluated. Parametric scanning has been performed by changing the phase difference between the coil currents in the two-phase traveling wave induction heater model, and the most appropriate phase difference values have been determined for different situations.İndüksiyon ısıtma hızlı, temassız, temiz, verimli, kolay ve hassas kontrol edilebilir bir ısıtma teknolojisidir. Bu özellikleri nedeniyle yüzey sertleştirme, temperleme, tavlama, kürleme gibi endüstriyel uygulamalarda; medikal uygulamalarda ve indüksiyon ocakları gibi evsel uygulamalarda sıklıkla tercih edilmektedir. İndüksiyon ısıtma sistemlerinde iş parçasının sıcaklığa bağlı olarak değişen parametreleri nedeniyle sistemin rezonans frekansı değişmekte ve verim düşmektedir. Bu tezde, indüksiyon ısıtma sisteminin sürekli rezonansta tutulması faz kilitli döngü (PLL) kullanılarak sağlanmıştır. Deri etkisinin azaltılması için indüksiyon bobini litz telinden yapılmıştır. Enine akı indüksiyon ısıtma sistemlerinde karşılaşılan iş parçasının orta kısımlarında yeterli ısı artışı oluşmama sorunu, iki fazlı yürüyen dalga indüksiyon ısıtıcı tasarımı ile çözülmüştür. Kaçak manyetik alanların azaltılması ve manyetik akının doğrudan iş parçasına yönlendirilmesi amacıyla ferrit manyetik akı yoğunlaştırıcı kullanılmıştır. Sayısal analizler 3 boyutlu modeller üzerinden sonlu elemanlar yöntemi kullanan COMSOL Multiphysics programı ile yapılmıştır. İlgili programda yoğunlaştırıcılı ve yoğunlaştırıcısız, tek ve çift bobinli enine akı indüksiyon ısıtma modellerinin karşılaştırması yapılmıştır. Sayısal analiz sonuçlarından enine akı indüksiyon ısıtma sistemlerinde iş parçası yüzeyinde homojen ısıtma için yürüyen dalga indüksiyon ısıtma ve manyetik akı yoğunlaştırıcı kullanılmasının sistemin performansını arttırdığı görülmüştür. Gerçekleştirilen indüksiyon ısıtma sistemi tarafından iş parçası üzerinde oluşturan sıcaklık değerleri termal kamera ile ölçülerek sistem performansı değerlendirilmiştir. Termal analizler Fluke Smartview programı kullanılarak yapılmıştır. İş parçası yüzeyinde oluşan sıcaklık değerlerinin minimum, maksimum, ortalama değerleri, standart sapmaları ve yataydaki iki eksen boyunca sıcaklık değişimleri incelenmiştir. Ayrıca seçilen bir noktanın belirli bir sıcaklığa ulaşma süresi değerlendirilmiştir. İki fazlı yürüyen dalga indüksiyon ısıtıcı modelinde bobin akımları arasındaki faz farkı değiştirilerek parametrik tarama yapılmış, farklı durumlar için en uygun faz farkı değerleri belirlenmiştir
Investigation of Wear and Corrosion Resistance of Wc-Coated Pearlitic Railway Steel in Dry and Wet Conditions
No full textIn this study, the effect of WC coating on the tribological performance of R260 rail steel was investigated by roller-on-plate wear tests and potentiodynamic polarisation corrosion tests carried out in dry and pure water environments. The High-Velocity Oxygen-Fuel (HVOF) method was used for the coating process. The tests were conducted with a weight of 40 N and a sliding speed of 0.03 m/s. An Ag/AgCl reference electrode was also used for corrosion tests in a 3.5 % NaCl solution. To produce cyclic polarisation curves, the experiments were carried out at a scan rate of 1 mV/s within a potential range of +/- 0.25 V. The effect of WC coating on the wear performance of rail steels was analysed quantitatively with the friction coefficient and volume loss parameters and visually with SEM and 2D-3D topography images. The effect of the coating on the corrosion performance was evaluated numerically with the corrosion potential, corrosion current intensity, and corrosion rate values, as well as elementally and visually with SEM and EDX images. Wear test results showed that the wear volume in WCcoated rail steels decreased by 43.07 % and 46.94 % compared to uncoated rail steels in dry and wet conditions. Corrosion test results showed that the corrosion rate of WC-coated rail steels was lower compared to uncoated rail steels, and the corrosive effect spread to a smaller area
Characterization of Epoxy Resin and Sille Stone Powder Based Composite Mortars
No full textSille stone, extracted from the Sille region of Konya (Türkiye) province, is an andesitic stone used in the construction of historical buildings. Sille stone is subject to deterioration due to long-term natural and environmental factors. Repair mortars are used to prevent damage to the stones used in the construction of historical buildings. In this study, Epoxy resin (ER)/Sille stone powder (SSP) composite mortars were produced for the restoration of historical buildings and the properties of these composite mortars were investigated. In the production of composite mortars were prepared by contributing SSP into epoxy resin in varied ratios such as 60-75% wt.%. When 60% SSP filler was added to the ER matrix, the compressive strength of the resulting composite increased by approximately 66% compared to neat ER. Moreover, an increase in mechanical strength and a decrease in water absorption were observed in composite mortars due to the increase in SSP. In conclusion, the high strength, low water absorption rate and pore properties of epoxy matrix composite mortars provide great potential for restoration applications of historical buildings constructed from Sille stone
Enhancing Mechanical Performance of Glass Fiber Reinforced Gypsum Composites With Carbon Black and Magnetite: an Integrated Optimization Approach
No full textToktas, Abdurrahim/0000-0002-7687-9061This study presents a comprehensive optimization methodology that integrates Taguchi Design of Experiments (Taguchi DoE), data augmentation, and the Cuckoo Search Algorithm (CSA) to improve the mechanical and electromagnetic characteristics of gypsum-based composites reinforced with carbon black, magnetite, and glass fiber. The effects of these additives on compressive and flexural strengths were evaluated using an L-16 orthogonal array, and optimal mixes were determined. The hybrid model attained a compressive strength of 32.23 MPa and a flexural strength of 1.41 MPa, demonstrating remarkable prediction accuracy (R-2 > 0.95). The integrated approach also allows cost-effective creation of multifunctional gypsum composites with improved mechanical and electromagnetic properties, in line with advanced construction material development.The authors gratefully acknowledge the Scientific and Technological Research Council of Turkey (TUBITAK) for support with grant number 221M271, and KMU BILTEM staff for their assistance and support.Scientific and Technological Research Council of Turkey (TUBITAK) [221M271
Sustainable Decolorization of Methyl Blue and Malachite Green From an Aqueous Environment Using Magnetic Biochar Prepared From the Fruit Seeds of Mespilus Germanica L
No full textThe purpose of this study was to assess the properties of nano-iron loaded biosorbent produced from Mespilus germanica L. fruits seed biochar (MGLfsB) powder, as well as the adsorption/desorption properties of two commonly used dyes; Methyl Blue (MB), and malachite green (MG). Mespilus germanica L. fruits seed biochar (nM-MGLfsB) was produced and used as a biosorbent to remove MB and MG from the solution. SEM and FT-IR analysis were used to characterize the prepared nM-MGLfsB. Temperature (303–333 K), pH (2.0–9.0), initial dye concentration (5–200 mg/L), nM-MGLfsB mass (0.1–0.9 g) and contact time (15–240 min) were all tested in batches to see how they influenced adsorption. The Freundlich, Langmuir, Scatchard, and Temkin models were used to analyze the equilibrium adsorption data. The Langmuir isotherm properly represented the adsorption data, and the saturated maximum removal of nM-MGLfsB determined using this model was 13.09 mg/g for MB and 28.33 mg/g for MG. For MB, nM-MGLfsB had a ΔS⁰ value of 63.974 and a ΔH⁰ value of 8.05; for MG, the values were 49.660 and 3.490, respectively. The results indicate that the nM-MGLfsB can effectively overcome the limitations of using nano-iron alone and achieve highly efficient dyes removal. © 2025 Informa UK Limited, trading as Taylor ; Francis Group
Performance Analysis of a Novel Directly Combined Organic Rankine Cycle and Dual-Evaporator Vapor Compression Refrigeration Cycle
No full textCombining Organic Rankine Cycles (ORC) with cooling cycles offers a promising approach to achieving greater outputs within a single system. In this study, a novel directly combined ORC-VCC system has been designed to not only meet the cooling demand using a geothermal heat source but also generate power. The proposed novel ORC-VCC system has been analyzed for its energetic performance using four selected fluids: R290, R600a, R601, and R1234ze(E). Parametric analysis has been conducted to investigate the effects of parameters of heat source temperature, heat source mass flow rate, cooling capacities, condenser temperature, ORC evaporator temperature, pinch point temperature difference and isentropic efficiencies on net power production. Among the working fluids, R290 has provided the highest net power production under all conditions in which it was available to operate. Additionally, the results have been analyzed concerning a reference cycle for comparative evaluation. The proposed novel cycle has outperformed the reference cycle in all investigated cases in terms of net power production such as demonstrating an improvement of approximately from 8.7% to 57.8% in geothermal heat source temperature investigations. Similar improvements have been observed over the reference cycle at lower heat source mass flow rates, where net power increases by up to 50.8%