Atılım Academic Archive (Atılım University)
Not a member yet
9347 research outputs found
Sort by
Outperformance of CaO-Incorporated Alumina-Supported Pd Catalysts in Methanol Decomposition
Get PDFThis study aimed to investigate the impact of CaO incorporation to alumina-supported Pd catalysts on the methanol decomposition reaction. For this purpose, mayenite, alumina and/or calcium oxide-supported Pd catalysts were synthesized. The synthesized catalysts were characterized by XRD, FTIR, Laser Raman spectroscopy, N2 adsorption-desorption, pyridine adsorbed DRIFTS, CO2-TPD, XPS, SEM-EDS, and ICP-OES techniques. Catalytic activity tests were carried out over a 6 h reaction period in the range of 100-400 degrees C. The results of the characterization and activity tests showed that the addition of CaO had significant effects on the physicochemical properties of the catalyst as well as on the catalytic activity. By adding CaO to the alumina support material, the acidity was reduced, thus reducing the selectivity for dimethyl ether (DME) formation, which is significantly high for the 1Pd@Al2O3 catalyst, and increasing the H2 and CO selectivity. The mayenite-supported catalyst (1Pd@SGM), which contains alumina and calcium oxide in its unique crystal structure, showed an excellent catalytic performance close to complete methanol conversion with DME selectivity below 1% at 400 degrees C. In the stability test carried out at 350 degrees C for 6 h with 1Pd@Al2O3, 1Pd@SGM, and 1Pd@48CaO@Al2O3 catalysts used in the temperature scan, it was concluded that all catalysts were stable and 1Pd@SGM catalyst showed higher catalytic activity than the others.Scientific and Technological Research Council of Turkiye (TUBITAK) BIDEB-2232 Program [118C237]; Gazi University Research Fund [FDK-2023-8907]; TUBITAKThis work was supported by the Scientific and Technological Research Council of Turkiye (TUBITAK) BIDEB-2232 Program (118C237), Gazi University Research Fund (FDK-2023-8907), TUBITAK-2211 PhD Scholarship Program, and TUBITAK-2250 Performance-Based Scholarships Program for PhD. The authors thank the Central Laboratory of METU, Central Laboratory of AYBU, and Atilim University Metal Forming Center of Excellence for the characterization results of the synthesized materials
Dynamic Market Efficiency Assessment in Sustainability Indices: Rolling Fractional Integration Analysis with Multiple Estimators
No full textThis study develops a comprehensive econometric framework for assessing market efficiency in sustainability indices through rolling fractional integration analysis. We employ four fractional integration estimators (Andrews-Guggenberger, Robinson GSE, GPH, and FELW) with formal statistical testing, addressing critical methodological gaps including single estimator dependency and static analysis approaches. Applied to 17 sustainability indices across 13 countries, our results reveal significant heterogeneity in market efficiency evolution. Developed markets exhibit timevarying efficiency patterns with periodic inefficiencies driven by institutional rebalancing dynamics, while emerging markets demonstrate superior efficiency characteristics. The BIST Sustainability Index exhibits exceptional efficiency, while the SP 500 ESG Screened Index shows the highest inefficiency levels among developed markets. The convergent validity between fractional integration and traditional unit root tests provides robust methodological validation. Our findings establish unprecedented robustness in sustainability market efficiency research while providing policy implications for financial regulators and investment managers
First Results From the Snd@lhc Experiment
No full textCentre de Physique Theorique de Grenoble-Alpes; et al.; Grenoble-Alpes Metropole; LPSC; Region Auvergne-Rhone-Alpes; Universite Grenoble AlpesSND@LHC started taking data at the beginning of Run 3 of the LHC. The experiment is designed to perform measurements with neutrinos produced in proton-proton collisions at the LHC in an energy range between 100 GeV and 1 TeV. It covers a previously unexplored pseudo-rapidity range of 7.2 < η < 8.4. The detector is located 480 m downstream of the ATLAS interaction point in the TI18 tunnel. The detector is composed of a hybrid system based on an 800 kg target mass of tungsten plates, interleaved with emulsion and electronic trackers, followed downstream by a calorimeter and a muon system. The configuration allows efficiently distinguishing between all three neutrino flavours, opening a unique opportunity to probe physics of heavy flavour production at the LHC in the region that is not accessible to ATLAS, CMS and LHCb. This region is of particular interest also for future circular colliders and for predictions of very high-energy atmospheric neutrinos. The detector concept is also well suited to searching for Feebly Interacting Particles via signatures of scattering in the detector target. The experiment has published several results. This work focuses on the experience gained from the first measurements and how this is being used to achieve the physics goals of SND@LHC. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0)
MO-ISCSO: A Challenging Benchmark Test Suite for Large-Scale Multi-Objective Structural Optimization
No full textCurrent studies on the development of multi-objective algorithms for optimization of truss structures mainly depend on small-scale classic benchmark instances. This paper highlights the importance of establishing standard large-scale multi-objective structural optimization benchmarking suites for accurate validation of the proposed algorithms. A new benchmark test suite, called MO-ISCSO, is proposed for large-scale multi-objective structural optimization, based on the most recent optimization problems of the international student competition in structural optimization (ISCSO). Owing to the very small feasibility ratios of the MO-ISCSO instances, the effect of presence of feasible designs in the initial population of NSGA-II, GDE3, and AR-MOEA multi-objective optimization algorithms is investigated using the proposed test suite. The obtained numerical results indicate that seeding the initial population with feasible solutions helps the foregoing algorithms maintain a better balance between convergence and diversity. The statistical results form a baseline for future studies on developing efficient multi-objective structural optimization techniques.Science Citation Index Expande
ISAR Imaging Of Drone Swarms Using Mmwave Radar
No full textTeknolojide drone ve drone sürülerinin kullanımının artmasıyla birlikte, anti-drone teknolojilerinin kullanımı önemli ölçüde artmıştır. Ancak, sınırlı görüş alanına sahip senaryolarda drone ve drone sürülerinin tespiti literatürde kalıcı bir zorluk olmaya devam etmektedir. Bu tez, milimetre dalga (mmWave) frekans bantlarında yeniden oluşturulan drone sürülerinin Ters Sentetik Açıklıklı Radar (ISAR) görüntülerinin, oluşumlarına, boyutlarına ve yük yapılandırmalarına göre sınıflandırılmasına odaklanmaktadır. Drone sürülerinin ISAR görüntüleri, ANSYS Yüksek Frekanslı Yapısal Simülatör (HFSS) elektromanyetik simülasyon yazılımı kullanılarak üretilmiştir. Sürü yapıları, quadcopter dronlar kullanılarak modellenmiş ve oluşum tipleri, çizgi, çarpı, kare ve üçgen gibi temel geometrik şekillerle tasarlanmıştır. Sürülerdeki dronlar, orta, küçük ve mini olmak üzere üç boyutta kategorize edilmiştir. Ek olarak, yük dronları sürü yapılandırmalarına dahil edilmiştir. Yüksek çözünürlüklü ISAR görüntüleri elde etmek için radar ve simülasyon parametreleri optimize edilmiştir. Veri setini genişletmek için, ISAR görüntüleri çeşitli bakış açılarında (0° ila 350° arasında 10° artışlarla) oluşturulmuştur. ISAR görüntüleri kullanılarak sürü oluşumu tiplerinin belirlenmesi, görüntü tanıma aşamasında bir Evrişimsel Sinir Ağı (CNN) aracılığıyla gerçekleştirildi. Bunu takiben, nesne algılama aşamasında Sadece Bir Kez Bak (YOLO) algoritması kullanılarak drone boyutu ve yük tespiti gerçekleştirildi. Bu tezde elde edilen sonuçlar oldukça ümit vericidir. Genişletilmiş bir veri seti ve tespit algoritması sunarak, bu çalışma literatüre önemli katkıda bulunmaktadır.With the increasing use of drones and drone swarms in technology, the importance of anti-drone technologies has grown significantly. However, detecting drones and drone swarms in scenarios with limited fields of view remains a persistent challenge in the literature. This thesis focuses on the classification of Inverse Synthetic Aperture Radar (ISAR) images of drone swarms reconstructed at millimeter-wave (mmWave) frequency bands based on their formation, size, and payload configurations. ISAR images of drone swarms were generated using the ANSYS High-Frequency Simulation Software (HFSS) electromagnetic simulation software. Swarm structures were modeled using quadcopter drones, and the formation types were designed with basic geometric shapes, such as line, cross, square, and triangle. The drones in the swarms were categorized into three sizes: medium, small, and mini. Additionally, payload drones were included in the swarm configurations. Radar and simulation parameters were optimized to obtain high-resolution ISAR images. To expand the dataset, ISAR images were reconstructed at various look angles (from 0° to 350° in 10° increments). The determination of swarm formation types using ISAR images was carried out through a Convolutional Neural Network (CNN) in the image recognition phase. The detection of drone size and payload configurations was conducted using the You Only Look Once (YOLO) algorithm in the object detection phase. The results achieved in this thesis are highly promising. By presenting an extended dataset and detection algorithm, this work contributes significantly to the literature and advances the field of drone swarm detection
Organ-Protective Effects of Fullerenol and Desflurane in a Rat Model of Ischemia-Reperfusion Injury
No full textYığman, Zeynep/0000-0003-1985-9280; Dursun, Ali Dogan/0000-0001-9056-0025To investigate the protective effects of fullerenol applied before ischemia induction and desflurane anesthesia applied during ischemia-reperfusion (IR) induction in the lungs and kidneys of a lower-extremity IR injury rat model. After receiving ethical approval, we randomly divided 30 rats into five groups: sham (S), IR, IR with 100 mg/kg fullerenol (IR-FUL), IR with 6.7% desflurane (IR-DES), IR with 100 mg/kg fullerenol and 6.7% desflurane (IR-FUL-DES). Fullerenol was administered 30 min before the IR procedure in the IR-FUL and IR-FUL-DES groups, and desflurane was administered during the IR procedure in the IR-DES and IR-FUL-DES groups. During the procedure, an atraumatic microvascular clamp was placed in the aorta for 120 min. The clamp was then removed to achieve reperfusion for 120 min. Finally, at the end of reperfusion, we evaluated the extracted lung and kidney tissue samples and assessed them biochemically and histopathologically. The lung damage scores of the IR-FUL, IR-DES, and IR-FUL-DES groups were significantly lower than those of the IR group (p < .0001, p = .002, and p < .0001, respectively). The renal tubule injury scores of the IR, IR-FUL, IR-DES, and IR-FUL-DES groups were significantly higher than those of the S group (p < .0001). By contrast, the renal tubule injury scores of the IR-FUL and IR-FUL-DES groups were significantly lower than those of the IR group (p < .0001 and p = .001, respectively). Moreover, kidney intercellular adhesion molecule 1 (ICAM1) expression was significantly lower in all the treatment groups, particularly the IR-FUL group, than in the IR group, and lung ICAM1 expression was significantly lower in the IR-FUL and IR-FUL-DES groups than in the other treatment groups. In the lung and kidney tissues, thiobarbituric acid reactive substance levels, catalase activity, glutathione-S-transferase activity, and arylesterase activity were relatively high in the treatment groups. The application of fullerenol before and after desflurane anesthesia during IR has protective effects on rat lungs and kidneys. In particular, histopathology confirmed that the application of fullerenol 30 min before IR induction and desflurane anesthesia during IR induction reduced oxidative stress and alleviated IR-related damage in the lungs and kidneys. These findings may have important translational relevance, suggesting potential perioperative strategies for protecting organs from ischemia-reperfusion injury in clinical settings
Araştırma ve Geliştirme Yatırımlarının Finansal Performansa Etkisi: UMS 38 Maddi Olmayan Duran Varlık Standardı Kapsamında Bir Değerlendirme
Get PDFTeknoloji ve inovasyonun giderek daha önemli hale geldiği günümüzde, işletmelerin sürdürülebilir başarı elde edebilmeleri için Araştırma ve Geliştirme (Ar-Ge) yatırımları kritik bir rol oynamaktadır. Ar-Ge yatırımları, işletmelerin uzun vadeli rekabet avantajını sağlama ve yenilikçi ürün geliştirme süreçlerinde ön plana çıkmaktadır. Bu bağlamda, işletmelerin sürdürülebilir iş modeli oluşturabilmek için bu değişimlere ayak uydurmaları gerekmektedir. Bu çalışmanın amacı işletmelerin küresel rekabet gücünü artırmak amacıyla gerçekleştirdikleri Ar-Ge harcamalarının ve yatırımlarının önemini vurgulamaktadır. Ar-Ge harcamalarının muhasebeleştirilmesi, UMS 38 Maddi Olmayan Duran Varlıklar Standardı çerçevesinde yapılan düzenlemelerle belirlenmektedir. UMS 38, Ar-Ge yatırımlarının gelecekte ekonomik fayda sağlaması durumunda maddi olmayan duran varlık olarak sınıflandırılmasını mümkün kılar. Ar-Ge yatırımlarının finansal performans üzerindeki etkisini incelemek için kapsamlı bir şekilde literatür taraması gerçekleştirilmiş ve bulgular, panel veri analizi yönteminin kullanılması ile desteklenmiştir. Araştırmada, Borsa İstanbul (BIST) 100 Endeksi'nde yer alan şirketler seçilmiştir. Seçilmiş olan şirketler yüksek Ar-Ge harcama potansiyeline sahip olmaları nedeniyle tercih edilmiştir. Çalışma, Ar-Ge yatırımlarının şirketlerin özsermaye kârlılığı (ROE), aktif kârlılık (ROA) ve piyasa değeri/defter değeri (PD/DD) gibi göstergelerine olan etkilerini analiz etmeyi amaçlamıştır. Bu çalışma, Ar-Ge yatırımlarının finansal performans üzerindeki etkilerini değerlendiren araştırmalar için önemli bir referans niteliği taşımaktadır ve işletmelere Ar-Ge harcamalarının muhasebeleştirilmesinde yol gösterici bir bakış açısı sunmaktadır.In the contemporary era, where technology and innovation are becoming increasingly significant, Research and Development (R&D) investments play a critical role in ensuring sustainable success for businesses. R&D investments stand out as essential in securing long-term competitive advantage and fostering innovative product development processes for enterprises. In this context, businesses must adapt to these changes to build sustainable business models. This study aims to emphasize the importance of R&D expenditure and investments undertaken by enterprises to enhance their global competitiveness. The accounting treatment of R&D expenditures is determined by regulations under the IAS 38 Intangible Assets Standard. IAS 38 allows the classification of R&D investments as intangible assets if they are expected to generate future economic benefits. To examine the impact of R&D investments on financial performance, an extensive literature review was conducted, and the findings were supported using panel data analysis methods. The study selected companies listed on the Borsa Istanbul (BIST) 100 Index, as these firms were chosen for their high potential for R&D expenditures. The study aims to analyze the impact of R&D investments on companies' financial performance indicators such as return on equity (ROE), return on assets (ROA), and price-to-book ratio (P/B). This research serves as a significant reference for studies evaluating the effects of R&D investments on financial performance and offers a guiding perspective for businesses in the accounting treatment of R&D expenditures
Experiences of Parents Who Have Children With Disabilities: A Qualitative Study From Türkiye During Covid-19
No full textThis study aimed to understand the experiences of parents who have young children with disabilities in Türkiye during COVID-19. We conducted a qualitative analysis of semistructured virtual interviews with eight parents. We used a collective within-case and across-case approach to analyze and interpret the interviews. Parents noted difficulties with the EI/ECSE programs and the need for individualized and functional services for their children. Furthermore, parents reported the need for high-quality, inclusive early childhood programs and the importance of well-trained educators. Parents also expressed interest in learning more about how to support their child's development and learning. Results may inform research, policy, and practice initiatives for children with disabilities and their families. The findings highlight the importance of including parent voices in the continued capacity-building efforts of EI/ECSE systems. Copyright © 2025 Wolters Kluwer Health, Inc. All rights reserved.Social Science Citation Inde
A Coupled Modelling and Simulation Approach to Electromagnetic Sheet Metal Forming
No full textThis study presents a coupled numerical and experimental investigation of electromagnetic forming (EMF) for aluminium sheets. A custom simulation framework is developed in ABAQUS/Standard using user-defined material (UMAT) and load (DLOAD) subroutines. The magnetic pressure exerted on the workpiece is computed through a finite difference-based solution of Maxwell's equations and applied to the mechanical solver. The mechanical response of the material is modelled using a strain-rate-sensitive plasticity law calibrated for aluminium 7075-O. Experimental forming trials are performed using a custom-built EMF setup, and the results are compared with numerical predictions to validate the model. The comparison shows strong agreement in deformation profiles, confirming the predictive capability of the proposed simulation strategy. This work offers a reliable computational tool for optimising EMF processes and provides insights into material behaviour under high strain rate electromagnetic loading.Scope of the TUBITAK 1005 project titled, "Design of a Warm/Hot Electromagnetic Forming System for the Forming of Brittle Sheet Metals" [215M929]; Scientific and Technological Research Council of Turkey (TUBITAK)The authors gratefully acknowledge the support of Prof. Dr. Elif Ayd1n within the scope of the TUBITAK 1005 project titled, "Design of a Warm/Hot Electromagnetic Forming System for the Forming of Brittle Sheet Metals" with project number 215M929. The authors also thank the Scientific and Technological Research Council of Turkey (TUBITAK) for funding this research.Emerging Sources Citation Inde