Mühendislik Fakültesi / Faculty of Engineering
Permanent URI for this collectionhttps://hdl.handle.net/11727/1401
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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 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 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 A New Approach to Fuzzy Initial Value Problem(2014) Gasilov, N. A.; Fatullayev, A. G.; Amrahov, S. E.; Khastan, A.; https://orcid.org/0000-0002-9955-8439; AEN-1756-2022In this paper, we consider a high-order linear differential equation with fuzzy initial values. We present solution as a fuzzy set of real functions such that each real function satisfies the initial value problem by some membership degree. Also we propose a method based on properties of linear transformations to find the fuzzy solution. We find out the solution determined by our method coincides with one of the solutions obtained by the extension principle method. Some examples are presented to illustrate applicability of the proposed method.Item Computational Prediction of MicroRNA Function and Activity(2014) Ogul, Hasan; 24272442Inferring microRNA (miRNA) functions and activities has been extremely important to understand their system-level roles and the mechanisms behind the cellular behaviors of their target genes. This chapter first details methodologies necessary for prediction of function and activity. It then introduces the computational methods available for investigation of sequence and experimental data and for analysis of the information flow mediated through miRNAs.Item Functional Copolymer/Organo-MMT Nanoarchitectures. XXII. Fabrication and Characterization of Antifungal and Antibacterial Poly (Vinyl Alcohol-co-Vinyl Acetate/ODA-MMT/AgNPs Nanofibers and Nanocoatings by e-Spinning and c-Spinning Methods(2015) Rzayev, Zakir M. O.; Erdonmez, Demet; Erkan, Kubra; Simsek, Murat; Bunyatova, Ulviye; 0000-0002-2904-3587Nanofibrous films and coatings were fabricated by electrospinning and centrifugal spinning of aqueous solutions of poly(vinyl alcohol-co-vinyl acetate)/octadecyl amine-montmorillonite layered silicate nanocomposites with/without in situ generated silver nanoparticles (AgNPs). Characterization of nanofibers were realized by FTIR, XRD, SEM, and thermal analysis methods. It was found that AgNPs significantly accelerated phase separation process providing fine distribution of nanofibers. Antifungal and antimicrobial activities of nanocomposites investigated by using Candida Spp fungals, G-positive and G-negative microorganisms strongly depended on chemical/physical structural factors, and loading silver species. Observed effective properties of nanomaterials can be employed for many applications (e.g., air filtration, food packaging, biomedical).Item The Effect of Organizational Culture on Implementing and Sustaining Lean Processes(2015) Pakdil, Fatma; Leonard, Karen Moustafa; 0000-0002-6299-6427; H-8189-2013Purpose - Lean systems thinking was widely studied using relevant variables, but there is a dearth of published theoretical or empirical evidence about the cultural aspects of lean processes. The lack of conceptual development is one of the motivations for this study. Do organizational cultural variations correlate with the success and effectiveness of lean processes? What organizational infrastructures are required for effective lean implementation and continuation? The paper aims to discuss these issues. Design/methodology/approach - Examining literature in the area of lean production and lean management, the authors sought current literature at the intersection of organizational culture and lean processes, particularly implementation and sustainability, but found little relating to the topic. Therefore, using the Competing Values Framework taxonomy, the authors examine this intersection, relying on related research in the areas. Findings - In this paper, a brief discussion of lean processes in relation to organizational culture leads to propositions that identify the various cultural dimensions and their purported effect on lean implementation and sustainability. A model of this interaction is developed. Those quadrants of the Competing Values Framework that might be useful in developing research directions for the future are identified. Research limitations/implications - Future research directions include the measurement of organizational culture in firms that have implemented lean processes. This would be a step toward looking at the effect that the different quadrants in the Competing Values Framework have on various elements of lean efforts. This would take a significant amount of work, because the manufacturing industry, the leader in implementing and sustaining lean processes, may have institutionalized particular organizational cultures. It would be an interesting step forward in the understanding of how lean processes are operationalized across different firms and industries. However, there are multiple ways to examine culture; the authors believe this method allows the capture of the entire spectrum. Practical implications - Knowing which dimensions influence lean effectiveness and the way that they wield that influence allows managers to develop the firm's organizational culture to one that will support implementing and sustaining lean efforts. The challenge to implement and sustain lean processes lies in the need to identify the organizational culture infrastructure that will allow this system that was first used by Japanese firms to operate well in other organizational contexts. The values and norms that underlie lean processes may create conflict with the culture that already exists within the organization; such divergence retards adoption and performance. Originality/value - There is a lack of research at the critical intersection of organizational culture and lean implementation/sustainability. Culture is key to making the changes required of lean implementation and in sustaining the drive toward lean production and management. The paper begins to fill that gap.