Mühendislik Fakültesi / Faculty of Engineering
Permanent URI for this collectionhttps://hdl.handle.net/11727/1401
Browse
183 results
Search Results
Item Intelligent Optimization Under the Makespan Constraint: Rapid Evaluation Mechanisms Based on the Critical Machine for the Distributed Flowshop Group Scheduling Problem(2023) Wang, Yuhang; Han, Yuyan; Wang, Yuting; Tasgetiren, M. Fatih; Li, Junqing; Gao, KaizhouIn the flowshop scheduling literature, the insertion-based neighborhood search method is often considered to obtain high-quality solutions. It will lead to expending extensive computational effort when evaluating the objective function. Rapid evaluation methods based on Taillard's acceleration can reduce the time complexity of function evaluation. However, existing rapid evaluation methods cannot be applied directly to the distributed flowshop group scheduling problem (DFGSP), especially to minimize the total tardiness time objective. Thus, we first proposed two theorems and their proofs based on the critical machine. Then, two rapid evaluation methods based on these theorems are proposed to accelerate the evaluation of the objective. Considering the multiple coupled sub-problems in the DFGSP, we proposed a cooperative iterated greedy algorithm (CIG) combining two rapid evaluation methods, in which intergroup and intra-group neighborhood search strategies are proposed to enhance the search depth and breadth. Comprehensive statistical experiments show that computational effort is extensively decreased in the calculation of total tardiness time, and the CIG algorithm significantly outperforms the eight compared algorithms.& COPY; 2023 Elsevier B.V. All rights reserved.Item Diver Detection and Tracking with Different Beamforming Algorithms(2023) Sevimli, Rasim A.Diver Detection Sonars (DDS) aim to detect the diver and tracking at the specific distance. At the side of signal processing case, there are bunch of beamforming algorithms to localize the target or diver in our case in the literature. In this paper, some beamforming algorithms are combined and compared via PSNR, time each other. Some algorithms show that the effect of sidelobes and reverberation are clearly decreased. Moreover, detection and tracking algorithms are applied to artificial sonar data created with a specific scenario for this purpose.Item Mechanical and Morphological Investigation of Laminated Composite Polymers Depending on Increasing Vibration Cycle(2023) Kemiklioglu, Ugur; 0000-0002-5597-1256Composite polymers are widely used in vibrating environments such as the aerospace, automotive, marine, and sports industries. Accordingly, composite materials are exposed to vibration at various periods. In this study, the effect of the vibration cycle on the mechanical properties of composite plates was investigated. The plates were vibrated at different revolutions. The tensile strength of these plates after vibration was examined, and these effects were compared with each other. As the vibration cycle increased, it was observed that tensile damage gradually occurred at different angles, and scanning electron microscopy (SEM) analysis revealed that the fibers were damaged at different angles. Accordingly, it was observed that the increased vibration cycle caused an angular fracture in the composite plates and decreased the tensile strength from 9.7 to 7.9 kN by nearly 23% as well as the elongation from 3.4 to 2.76 mm.Item Toward Camouflage Colors by Electrochemical Copolymerization(2023) Ergun, Emine Gul Cansu; Carbas, Buket BezginIn this paper, a new electrochromic copolymer containing 6,9-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-1,2,3,4-tetrahydrophenazine (EBE) and 4-(9-benzyl-9H-carbazol-3-yl)-7-(thiophen-2-yl)benzo[c][1,2,5]thiadiazole (CBT) in the main chain was reported. The homopolymers, (Poly(EBE) and Poly(CBT)), were also prepared via electrochemical polymerization and their electrochemical, spectroelectrochemical and electrochromic properties were analyzed in order to compare their properties with those of copolymer (Poly(EBE-co-CBT)). The copolymer exhibited good switching property for military camouflage necessities with color change from hues of brown to green. Furthermore, it has been tried to analyze the effects of combination of two donor-acceptor-donor (DAD) type monomers with different symmetries on the copolymer properties. A viable strategy for electrochromic adaptive camouflage was presented. New electrochromic copolymer film containing 6,9-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-1,2,3,4-tetrahydrophenazine and 4-(9-benzyl-9H-carbazol-3-yl)-7-(thiophen-2-yl)benzo[c][1,2,5]thiadiazole in the main chain was synthesized using electrochemical polymerization technique. The resulting copolymer film matched the military camouflage necessities with having color changes from hues of brown to green. Moreover, an "asymmetric and symmetric donor-acceptor-donor type monomeric combination" in an electrodeposited copolymer film was first time presented.imageItem Electrochromic Insight on Electro-Deposited Copolymers of Push-Pull Conjugated Systems with 3,4-Ethylenedioxythiophene (EDOT) and Other Conjugated Units(2023) Ergun, Emine Gul Cansu; Hacioglu, Serife OzdemirThird generation conducting polymers (CP) are push-pull type conjugated systems, which include both electron pushing and pulling units in their chemical structure. Push-pull design enables coarse and fine tuning in the electro-optical properties of the resulting CP such as lowering the band gap and enhancing electrochromic properties. Push-pull CPs have been widely used for various applications such as electrochromic devices, displays, light emitting diodes, organic solar cells, field effect transistors, electrochemical and optical sensors etc. This review aims to collect electrochemically synthesized CPs of push-pull systems in the literature, up to 2023. Most of the studies include 3,4-ethylenedioxythiophene (EDOT) as co-monomers, but there are also other studies such as obtaining push-pull type CPs by copolymerization, and copolymerization of push-pull systems with other units. Each case is discussed in separate sections. In the scope of this review, only electrochemical copolymerization studies are selected, and the effect of monomer feed ratio and the polymerization conditions on the electrochromic properties of the resulting copolymers are discussed and summarized in tables. This collection can serve as a guide for upcoming copolymerization studies, by giving an insight into optical and electrochromic properties of various copolymers of push-pull systems so far. A comprehensive literature survey about electrochemical copolymerization of push-pull type conjugated systems with 3,4-ethylenedioxythiophene (EDOT) and other conjugated units. Effect of monomer feed ratio and polymerization conditions on the electrochromic properties of resulting copolymers were discussed.imageItem RadGT: Graph and Transformer-Based Automotive Radar Point Cloud Segmentation(2023) Sevimli, Rasim A.; Ucuncu, Murat; Koc, Aykut; 0000-0002-2113-1398; KDO-6837-2024The need for visual perception systems providing situational awareness to autonomous vehicles has grown significantly. While traditional deep neural networks are effective for solving 2-D Euclidean problems, point cloud analysis, particularly for radar data, contains unique challenges because of the irregular geometry of point clouds. This letter proposes a novel transformer-based architecture for radar point clouds adapted to the graph signal processing (GSP) framework, designed to handle non-Euclidean and irregular signal structures. We provide experimental results by using well-established benchmarks on the nuScenes and RadarScenes datasets to validate our proposed method.Item Multimodal Video Captioning Using Object-Auditory Information Fusion with Transformers(2023) Selbes, Berkay; Sert, MustafaVideo captioning aims to generate natural language sentences of an input video. Generating coherent natural language sentences is a challenging task due to the complex nature of video content such as object and scene understanding, extraction of object- and event-specific auditory information, and acquisition of relationships among objects. In this study, we address the problem of efficient modeling of object interactions in scenes, as they include crucial information regarding the events in the visual scene. To this end, we propose to use object features along with auditory information to better model the audio-visual scene appearing within the video. Specifically, we extract Faster R-CNN as the object features and VGGish as the auditory features and design a transformer encoder-decoder architecture in the multimodal setup. Experiments on MSR-VTT show encouraging results and object features better model the object interactions along with the auditory information in comparison to the ResNet features.Item Six Sigma Project Prioritization and Selection Using AHP-CODAS Integration: A Case Study in Healthcare Industry(2023) Can, Gulin Feryal; Toktas, Pelin; Pakdil, Fatma; https://orcid.org/0000-0001-6622-4646; D-7271-2018Given the complex nature of Six Sigma project (SSP) prioritization and selection processes, multicriteria decision-making (MCDM) methods may help organizations identify the most effective projects. Considering potential limitations of subjective methods and advantages of MCDM methods, this article proposes a model that integrates analytical hierarchy process (AHP) and combinative distance-based assessment (CODAS) in SSP prioritization and selection process. In the proposed approach, AHP is employed to assign criteria weights, and CODAS is performed to determine priorities of SSPs. CODAS was advanced in term of its threshold function. Differences between Euclidean distances of two alternatives were compared, based on the standard deviation of Euclidean distances of all alternatives to overcome the subjectivity. This is the first study that combines AHP and CODAS methods for SSP selection, and CODAS is used with objective threshold value computation, and developed for the healthcare industry. In this article, ten SSPs were evaluated for four key criteria groups as financial, operational, patient centric, and organizational main criteria groups. In total, 18 subcriteria were considered under these four main criteria groups. This article provides a support for executives who make implementation plans for the potential SSPs.Item Beam Steering of Vortex Waves by A Phased Array Based on The Field Equivalence Principle(2022) Hizal, Altunkan; Yildiz, HayrullahA further ability can be added to an existing phased array (PA) to include generation and steering of noncollimated or collimated electromagnetic (EM) vortex waves (VW). The concept is based on the EM field equivalence principle. The near field of VW's generated by a uniform circular array (UCA) is calculated on a tilted planar finite size reference aperture (RAP) which intercepts all the VW modes. Using the Love equivalence principle and the fields of UCA on the RAP, the VW's are calculated in the far field. RAP is divided into small rectangular subapertures (SAP), simulating the elements of a PA. The UCA-fields on each SAP, for a given RAP's tilt angle (steering angle) are calculated. These fields are to be generated by rightly polarized PA's antenna elements fed by the associated transmit-receive modules. The method is also applied to VW's tightly collimated by a paraboloidal reflector. Numerical simulations obtained verified this concept.Item Stokes Flow in Lid-Driven Cavity Under Inclined Magnetic Field(2022) Gurbuz-Caldag, M.; Celik, E.; https://orcid.org/0000-0002-7746-9005; HLG-7277-2023STOKES FLOW IN A LID-DRIVEN CAVITY under the effect of an inclined magnetic field is studied. The radial basis function (RBF) approximation is employed to the magnetohydrodynamic (MHD) equations which include Navier-Stokes equations of fluid dynamics and Maxwell's equations of electromagnetics through Ohm's law with the Stokes approximation. Numerical results are obtained for the moderate Hartmann number (0 < M < 80) and different angles of a magnetic field (0 < alpha < pi). It is found that the increase in the Hartmann number causes the development of new vortices under the main flow due to the impact of a magnetic field. However, the type of the inclination angle (acute or obtuse) determines the location of the vortices.