https://hdl.handle.net/20.500.12809/1 Research Outputs | TR-Dizin | WoS | Scopus | PubMed 2026-06-23T03:21:45Z https://hdl.handle.net/20.500.12809/11207 Regularized Cox Models Versus Deep Survival Networks in Low Events-per-Variable Regimes: A Benchmark Across Censoring Levels Yılmaz, Ersin Survival analysis on biomedical data has seen quick methodological growth, but practitioners face limited guidance on which family of methods to prefer when censoring rates are high or the ratio of predictors to events is unsuitable. This paper presents a systematic benchmark of six survival models-the classical Cox model, lasso-penalized Cox, the Bayesian elastic net Cox model (BEN-Cox), random survival forests, DeepSurv, and Cox-Time-across three publicly available datasets (METABRIC, SUPPORT, and TCGA-BRCA) under controlled censoring regimes. The experimental grid scans events-per-variable (EPV) ratios from 0.6 to 7.6 and censoring rates from 33% to 86%. Performance is evaluated using Harrell's concordance index, time-dependent concordance, the integrated Brier score, and the calibration slope, with statistical comparisons carried out by paired Wilcoxon signed-rank tests with Holm correction. Three main findings are obtained. First, BEN-Cox, lasso-Cox, and random survival forests form a narrow top tier in discrimination, with pooled C -index values within 0.003 of each other, while DeepSurv and Cox-Time do not reach this tier in any configuration. Second, calibration separates models that discrimination does not: BEN-Cox achieves the lowest integrated Brier score in all six configurations, while lasso-Cox produces calibration slopes closest to one on the high-dimensional datasets; deep models and the unpenalized Cox model are systematically overconfident. Third, increasing censoring widens the gap between the regularized top tier and the deep architectures without changing which model family is preferred. An empirical partition of the (c, EPV) plane summarizes these observations. Because the entire grid falls below the classical EPV threshold of ten, the partition documents the low-EPV regime in which regularized models dominate but does not identify the boundary at which deep models may become competitive. 2026-01-01T00:00:00Z https://hdl.handle.net/20.500.12809/11206 Sustainable biodiesel from an invasive fish using immobilized lipase on magnetic nanogels as a novel management approach Saç, Gülşah; Arabacı, Gökmen; İspirli Doğaç, Yasemin; Çağan, Aleyna; Ağdamar, Sevan; Özuluğ, Müfit An alternative strategy to mitigate the ecological and economic challenges posed by invasive fish species is to transform these organisms into valuable resources, generating economic benefits while simultaneously addressing ecosystem-related concerns. However, while the search for sustainable feedstocks continues, the specific potential of highly resilient invasive fish species for high-yield biodiesel production has not yet been evaluated. The aim of this study was to address this research gap by producing high-yield biodiesel using the invasive fish Carassius gibelio as an oil source. In this context, lipase immobilized MnFe2O4- polyhydroxymethyl methacrylate magnetic nanogels were prepared and the production system conditions (lipase amount, methanol/oil molar ratio, and temperature) were optimized. Optimal conditions were obtained using a 4000 U lipase amount, a 5:1 methanol/oil molar ratio and a temperature of 55 °C. A 97.45% biodiesel yield was achieved with this system prepared under optimum conditions, and this prepared biocatalysis system was able to produce biodiesel with at least 50% yield 13 times. This study is the first to use the highly invasive C. gibelio as a sustainable raw material for biodiesel production. It introduces a novel biocatalytic approach by integrating invasive fish species utilization with a reusable MnFe2O4-pHEMA nanogel system, achieving both high efficiency and operational stability. 2026-01-01T00:00:00Z https://hdl.handle.net/20.500.12809/11205 Beyond Efficiency: Testing DEA -Selected Portfolios with Behavioral Utility and the Sharpe Ratio in BIST 100 Cenger, Hatice The study aims to empirically test the superiority of portfolios composed of stocks located on the DEA efficient frontier and introduces a multidimensional evaluation framework that integrates technical efficiency analysis with investor behavior. The risk-return space, based on Markowitz’s mean-variance model, is non-parametrically restructured using Data Envelopment Analysis (DEA). Portfolios constructed based on DEA super-efficiency scores are evaluated using a utility function representing investor preferences modeled within a behavioral finance framework (A = 1 and A = 5); performance is also compared via the Sharpe ratio. The analysis, conducted using BIST 100 data for the period 2016-2019, shows that the highest utility and Sharpe ratios are concentrated in portfolios identified by DEA as efficient. These findings suggest that technical efficiency and behavioral investment decisions can align, providing investors with a holistic framework for both rational and behaviorally consistent portfolio selection. 2026-01-01T00:00:00Z https://hdl.handle.net/20.500.12809/11075 Raffaello Sanzio’dan Önce Ahmedi Vardı: Osmanlı Devleti’nde Ekfrastik Bir Atina Okulu Tablosu ya da Felsefenin Şiirleştirilmiş Hali İnce, Yunus In his work titled Iskendername, the last copies of which are dated to 1411, Ahmedi describes in an ekphrasis style the discussions of Greek philosophers in the presence of Alexander on philosophical issues such as the essence of existence, its types, and the source and end of existence. In Iskendernâme, a method that aims to reach a conclusion through the comparison of opposing concepts such as limited will-major will, soul-body, world-ukba, youth-age, creator-created, wahdat-continuity, and intellect-nafis is adopted. In the work, philosophers such as Socrates, Plato, Aristotle and Hippocrates represent Greek/Western philosophy, while the unnamed Indian philosopher and the Chinese philosopher named Behram represent Eastern philosophy, and Khidr represents divine theology or Islamic philosophy. The painting known as the School of Athens, on the other hand, is a fresco completed by Raffaello Sanzio in 1511 upon papal commission to show the reconciliation of philosophy and theology. The Greek philosophers depicted arguing among themselves in the work represent Western philosophy. This study aims to compare two works, one produced in the form of poetry and the other in the form of a painting, which deal with the same subject approximately a century apart, in terms of their understanding of philosophy and esthetics. By subjecting both works to a comparison in terms of art and philosophy, it will be possible to draw attention to the differences between the Western and Eastern Civilizations’ understanding of art and philosophy. More detailed studies are needed to determine all the details of the two civilizations’ views on art and philosophy.; Ahmedî, son nüshaları 1411 yılına tarihlenen İskendernâme adlı eserinde Yunan filozoflarının İskender’in huzurunda varlığın özü, türleri, varlığın kaynağı, sonu gibi felsefî konulardaki tartışmalarını ekfrastik bir tarzda betimler (şiirle resmeder). İskendernâme’de cüzi irade-külli irade, ruh-beden, dünya-ukba, gençlik-yaşlılık, yaratıcı -yaratılmış, vahdet-kesret, akıl-nefis gibi zıt anlamlı kavramların karşılaştırılması üzerinden neticeye ulaşmayı hedefleyen bir usul benimsenmiştir. Eserde Sokrates, Platon, Aristoteles, Hipokrates gibi filozoflar Yunan/Batı felsefesini temsil ederken, adı zikredilmeyen Hintli filozof ve Behram adlı Çinli filozof Doğu felsefesini, Hızır ise ilahî kelamı ya da İslâm felsefesini temsil eder. Atina Okulu olarak bilinen resim ise, Rafaello Sanzio tarafından Papalığın felsefe ile teolojiyi uzlaşı içerisinde göstermek için 1511 yılında tamamlanmış bir fresktir. Bu freskte farklı hatta zıt görüşte olan filozoflar belirli gruplara ayrılmış şekilde bir arada resmedilmiştir. Eserde kendi aralarında tartışır vaziyette resmedilen Yunan filozofları, Batı felsefesini, İbn Rüşd ve Zerdüşt, Doğu felsefesini temsil eder. Bu çalışma yaklaşık yüzyıl arayla aynı konuyu işleyen biri şiir diğeri ise resim formunda üretilmiş iki eseri, felsefe ve estetik anlayışları bakımından karşılaştırmak amacındadır. Her iki eserin sanat ve felsefe açısından bir karşılaştırmaya tabi tutulmasıyla, Batı ve Doğu medeniyetlerinin sanat ve felsefe anlayışları arasındaki farklara dikkat çekmek mümkün olacaktır. İki medeniyet dairesinin sanata ve felsefeye bakışı hususundaki tüm ayrıntıların tespiti hususunda daha ayrıntılı çalışmalara ihtiyaç bulunmaktadır 2025-01-01T00:00:00Z