Akademik Arşiv / Academic Archive
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Publication A Vibrational Spectroscopic Investigation of 2,2'-Bithiophene Using Experimental and DFT Methods(2023)Organic compounds like 2,2’-Bithiophene (with a synonym. 2,2'-bithienyl, 2,2'-dithienyl)- containing bis(dioxaborin) have drawn significant concern in the area of materials science because of their electron affinity and luminescent properties. With this motivation, we have been concentrating on the properties and functions of 2,2'-Bithiophene.Publication Multi-objective location-distribution optimization in blood supply chain: an application in Turkiye(2024-11-15) Altunoğlu, Burcu; Batur Sir, Gül DidemPurpose Blood donors are crucial in maintaining the blood supply chain. This study aims to improve the location and distribution of blood donation centers by focusing on two main objectives: minimizing costs and maximizing quality. Minimizing costs includes setting up and transporting blood efficiently while maximizing quality to ensure that blood products are delivered to hospitals promptly and in the right quantities. Methods A multi-objective mathematical model is proposed to address the placement of both fixed and mobile blood donation centers. The first objective focuses on minimizing the costs of setting up centers and transporting blood. The second objective aims to maximize quality by ensuring timely deliveries and meeting hospitals’ blood demand. The model utilizes real-world traffic and blood donation data from urban settings to simulate its effectiveness and applicability in practice. The model uses the epsilon constraint method to optimize both objectives simultaneously. Results The model was tested in various scenarios, optimizing cost and quality separately. The algorithm determined the ideal locations for blood donation centers to meet demand by exploring different options. It also accounted for factors that reduce quality, such as delayed deliveries and product returns, and showed that these issues could be minimized. Conclusion This study highlights the need to balance cost and quality when determining the locations of blood donation centers. Using the epsilon constraint method, the model successfully optimized both objectives, offering valuable insights for improving the efficiency and effectiveness of blood donation operations.Publication One Dof Thumb Mechanism and It's Dimensional Optimization(International Journal of Multidisciplinary Studies and Innovative Technologies, 2019-01-01) Yavuz, SametThis paper involves the geometrical representation, kinematic solution and dimensional optimization of a one degree of freedom parallel thumb mechanism. The aim of the designing of this mechanism grasping objects by mimicking of a human thumb. Link length optimization of the mechanism are made around an average human thumb sizes by using Firefly Algorithm which is a nature inspired optimization algorithm.Publication Development of a Restraint System for Rear-Facing Car Seats(Machines, 2023-01-01) Himmetoğlu, Selçuk; Yavuz, SametIn self-driving vehicles, passengers can set their seats in an unconventional seating position, such as rear-facing. Sitting in such an orientation can increase the risk of whiplash in the head-and-neck system in a frontal impact, as frontal crashes usually have higher severities compared with rear-end crashes. This paper shows that a forward-facing front seat optimised for rear-impact protection needs to be redesigned to be used as a rear-facing seat. In the second and main part of this paper, a restraint system for rear-facing car seats is developed, and frontal impact simulations with 64 km/h of delta-V are used to evaluate its performance. The designed seating system comprises two rigid torso plates, a fixed recliner and an energy absorber under the seat pan. Without using the developed restraint system, the 50th percentile male human model is exposed to neck shear forces exceeding 600 N. With the developed restraint system, neck shear forces are less than 350 N in frontal impacts with 64 km/h of delta-V. Apart from whiplash, the risk of head, chest, lower extremity and lower back injuries are also evaluated. The results confirm that the developed restraint system successfully protects the occupant since all assessment criteria values are lower than the injury assessment reference values.Publication Improvement of breakdown characteristics in AlGaN/GaN/AlxGa1 xN HEMT based on a grading AlxGa1 xN buffer layer(2010-01-01) Kelekçi, ÖzgürTo improve the breakdown characteristics of an AlGaN/GaN based high electron mobility transistor (HEMT) for high voltage applications, AlGaN/GaN/AlxGa1 xN double hetero structure (DH-HEMTs) were designed and fabricated by replacing the semi-insulating GaN buffer with content graded AlxGa1 xN(x¼x1!x2, x1>x2), in turn linearly lowering the Al content x from x1¼90% to x2¼5% toward the front side GaN channel on a high temperature AlN buffer layer. The use of a highly resistive AlxGa1 xN epilayer suppresses the parasitic conduction in the GaN buffer, and the band edge discontinuity limits the channel electrons spillover, thereby reducing leakage current and drain current collapse. In comparison with the conventional HEMT that use a semi-insulating GaN buffer, the fabricated DH-HEMT device with the same size presents a remarkable enhancement of the breakdown voltage.