Scopus İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395

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  • Article
    Failure Analysis of Fused Deposition Modeling 3D Printed Poly Lactic Acid Polymer
    (Sage Publications Ltd, 2025-10-04) Yilmaz, Cagatay; Eltahir, Sara Saeed Abdulrahman
    Additive manufacturing, commonly known as 3D printing (AM), has emerged as one of the most transformative technological advances in the last few decades in global manufacturing, as it allows for the production of intricate components without the use of costly molds. Fused Deposition Modeling (FDM) is widely adopted among various AM techniques due to its accessibility and effectiveness. FDM 3D-printed PLA (Poly Lactic Acid) shows a transversely isotopic symmetry similar to laminated composite structures. Therefore, classical lamination theory can be applied to FDM 3D-printed PLA. This study attempts to expand the knowledge by relying on classical lamination theory and several imposed failure theories like maximum stress, Tsai-Hill, Tsai-Wu, and Hashin to determine how FDM 3D printing of PLA fails. We investigate eight different raster orientations (0 degrees, 10 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees, and 90 degrees) and compare the theoretical prediction of strength with experimental findings. With this comprehensive analysis, we are seeking to better understand the failure analysis of FDM 3D printed PLA. The maximum stress, Tsai-Wu, Tsai-Hill, and Hashin failure theories show good agreement with experimental findings for 0 degrees and 90 degrees raster orientations. As the raster orientation shifts from 0 degrees, the discrepancy between experimental results and theoretical predictions increases, peaks at mid-angles, and then decreases, becoming negligible at 90 degrees.
  • Article
    Citation - WoS: 6
    Citation - Scopus: 4
    Towards Global Sustainable Development: The Role of Financial Innovation and Technological Advancements
    (Sage Publications Ltd, 2024-08-10) Dogan, Eyup; Chishti, Muhammad Zubair; Zaman, Umer; Binsaeed, Rima H.
    The importance of metaverse and blockchain technologies in today's global landscape cannot be overstated. These innovative technologies offer transformative potential for various sectors, including economics, by enhancing connectivity, security and transparency. The present study leverages these technologies to investigate their dynamic impacts, in conjunction with geopolitical risk, on global economic cycles to navigate the challenges of an interconnected world. To ensure the reliability of our findings, this study employs two proxies to gauge economic cycles: global green economic growth and global environmental sustainability. By utilizing daily data, this study reveals several noteworthy findings. First, the quantile-var-based network analysis demonstrates a robust directional connection among the variables in our model. Second, the wavelet quantile correlation technique uncovers the significant role of metaverse technology in influencing economic cycles by promoting global green economic growth and global environmental sustainability across all time horizons (short, medium and long term). Third, economic cycles exhibit a negative association with financial innovation and a positive connection with geopolitical risk across all timeframes. Fourth, the continuous wavelet transform causality test identifies a substantial causal relationship running from metaverse technology, financial innovation and geopolitical risk to economic cycles. Based on our empirical results, this study recommends that the global economy should continue investing in metaverse and blockchain technologies to address economic cycles in the future.
  • Article
    Citation - WoS: 7
    Citation - Scopus: 11
    Robust Estimator-Based Optimal Control Designs for U-Tube Steam Generators
    (Sage Publications Ltd, 2014-05-19) Ablay, Gunyaz; Hamamci, Serdar
    U-tube steam generator level control systems are used to maintain the water level within prescribed narrow limits and to provide constant supply of high-quality steam during power demand variations. Traditional level control systems are often found to be unsatisfactory during low power operations and start-up conditions. Robust non-linear estimator-based optimal control systems are proposed for steam generator level control systems to solve the water level tracking problem during power (or steam) demand variations. It is shown that the proposed control strategies provide optimal and robust water level tracking with a single controller over the complete range of power operation with model and parameter uncertainties and noisy measurements.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 5
    Large Transformations With Moderate Strains of Tensile Membrane Structures
    (Sage Publications Ltd, 2016-04-28) Beatini, Valentina; Carfagni, Gianni Royer; Royer Carfagni, Gianni
    Using a classical non-linear theory, we analytically investigate possible ways for transforming the shape of a curved elastic membrane while keeping it tensioned and moderately strained. This is a critical issue because, as a rule, membranes must be considerably stretched in order to avoid wrinkling and slackening. If the final configuration is fixed, the membrane can be cut and formed according to the final shape, but this cannot be done if more configurations, considerably distant from one another, have to be achieved. Nevertheless, we propose large transformation movements that can be obtained starting from flat membranes while maintaining their strain as limited. We discuss in detail the paradigmatic example of the hyperbolic-paraboloid-shaped membrane. These opportunities are suitable for applications of transformable architecture because they do not require excessive tensioning, compatible with the strength of materials used for this kind of structures.
  • Article
    Citation - WoS: 3
    Citation - Scopus: 3
    Investigations of Strain Rate, Size, and Crack Length Effects on the Mechanical Response of Polycaprolactone Electrospun Membranes
    (Sage Publications Ltd, 2021-06-18) Bayram, Ferdi C.; Kapci, Mehmet F.; Yuruk, Adile; Isoglu, Ismail A.; Bal, Burak
    The effects of strain rate, size (height x width), and pre-existing crack length on the mechanical response of polycaprolactone electrospun membranes were investigated by tension tests conducted at room temperature. In particular, tensile tests were performed with three different strain rates for strain rate effect tests, seven different geometries for elucidating the size effect, and three different initial notch lengths for crack growth experiments. The electrospun membranes were produced by the electrospinning technique using a polycaprolactone solution prepared in 1, 1, 1, 3, 3, 3-hexafluoro-2-propanol as the solvent. Scanning electron microscopy was utilized to show the continuous fiber structure without bead formation. The average fiber diameter was calculated as 1.113 +/- 0.270 mu m by using scanning electron microscopy images of the membranes. The chemical structure of polycaprolactone was analyzed by Fourier transform infrared spectroscopy, and the toxicity and cell viability of the electrospun membranes were shown by CellTiter 96(R) Aqueous One Solution Cell Proliferation Assay (MTS test). It was observed that the ultimate tensile strength and Young's modulus decreased, and the elongation at failure value increased as the strain rate decreased from 10(-1) to 10(-3) s(-1). Besides, positive strain rate sensitivity was observed on the mechanical response of electrospun polycaprolactone membranes. Moreover, the dependency of mechanical response on the size geometry has been well studied, and the optimum height and width combinations were specified. Also, crack growth was studied in terms of both macroscopic and microstructural deformation mechanisms and it is observed that individual fiber deformations and interactions are highly effective on the mechanical behavior and also propagation of the crack. Consequently, in this study, the size and strain rate effects and crack growth on the mechanical response of electrospun polycaprolactone membranes have been investigated extensively, and the results presented herein constitute an essential guideline for the usage of polycaprolactone electrospun membranes at different loading scenarios.
  • Article
    Citation - WoS: 12
    Citation - Scopus: 13
    Implementation of Cost Benefit Analysis of Vehicle to Grid Coupled Real Micro-Grid by Considering Battery Energy Wear: Practical Study Case
    (Sage Publications Ltd, 2020-10-07) Koubaa, Rayhane; Yoldas, Yeliz; Goren, Selcuk; Krichen, Lotfi; Onen, Ahmet
    The proposed research represents a spin-off of the Malta College of Arts, Science and Technology (MCAST) Micro-Grid (MG) project. Particularly, economic impact of Electric Vehicles (EV) integration into the MG is investigated in this paper. The MCAST MG consists of photovoltaic generation unit, a diesel generator and a battery storage system. In this paper, a Vehicle-to grid (V2G) concept is considered where utilities can profit from controlled energy trading operations according to EVs availability. EVs are categorized under different profiles considering energy and time availability of owners typical work hours. V2G energy cost is estimated based on battery energy wear due V2G extra cycling and refunded to EVs owners. As most of developed V2G studies don't consider real world input data or/and EV battery aging cost in system modeling and evaluation, the present paper presents a reliable study as it considers a real life MG with in field measurement input data and appropriate battery degradation model. The adopted model represents a linear approximation with a minimum error value to make a suitable tradeoff of computational complexity and accuracy of obtained results. Economic assessment of the system according to the proposed energy management is performed, where results indicate that the V2G system assisted the MG operation during high electricity price period and achieved economic profit to EVs owners. According to numerical results, V2G energy trading achieved 29.90 EUR of gross selling revenues with only 4.46 EUR as battery degradation cost which makes a 16.41% average cost reduction of daily MG operation cost.
  • Article
    Citation - WoS: 81
    Citation - Scopus: 124
    Gender and Sexuality in the Authoritarian Discursive Strategies of 'New Turkey
    (Sage Publications Ltd, 2016-11-18) Cindoglu, Dilek; Unal, Didem
    In the last decade, discourse on sexuality has proliferated more than ever in the political realm in Turkey. The discursive utilization of women's bodies and sexualities has appeared as the main tool to consolidate a conservative gender regime and the heterosexual family with children is promoted as the basic unit to reinforce hegemonic moral values and norms. This article aims to disentangle the intricate patchwork in the Justice and Development Party's (JDP) gender politics, which is geared towards ensuring pervasive control of women's bodies and sexualities. Within this framework, this article investigates the proliferation of the discourse on women's bodies and sexualities in Turkish politics by delving into the constitutive factors of the JDP's hegemonic gender politics and examining the narrative lines in recent public debates on women's sexualities.
  • Article
    Citation - WoS: 40
    Citation - Scopus: 49
    Fisetin and Hesperetin Induced Apoptosis and Cell Cycle Arrest in Chronic Myeloid Leukemia Cells Accompanied by Modulation of Cellular Signaling
    (Sage Publications Ltd, 2015-09-25) Adan, Aysun; Baran, Yusuf
    Fisetin and hesperetin, naturally occurring flavonoids, have been reported as novel antioxidants with chemopreventive/chemotherapeutic potential against various types of cancer. However, their mechanism of action in CML is still unknown. This particular study aims to evaluate the therapeutic potentials of fisetin and hesperetin and their effects on cell proliferation, apoptosis, and cell cycle progression in human K562 CML cells. The results indicated that fisetin and hesperetin inhibited cell proliferation and triggered programmed cell death in these cells. The latter was confirmed by mitochondrial membrane depolarization and an increase in caspase-3 activation. In addition to that, we have detected S and G2/Mcell cycle arrests and G0/G1 arrest upon fisetin and hesperetin treatment, respectively. To identify the altered genes and genetic networks in response to fisetin and hesperetin, whole-genome microarray analysis was performed. The microarray gene profiling analysis revealed some important signaling pathways including JAK/STAT pathway, KIT receptor signaling, and growth hormone receptor signaling that were altered upon fisetin and hesperetin treatment. Moreover, microarray data suggested potential candidate genes for targeted CML therapy. Fisetin and hesperetin significantly modulated the expression of genes involved in cell proliferation and division, apoptosis, cell cycle regulation, and other significant cellular processes such as replication, transcription, and translation. In conclusion, our results suggest that fisetin and hesperetin as potential natural agents for CML therapy.
  • Article
    Citation - WoS: 3
    Citation - Scopus: 5
    Feedback Controller Designs for an Electromagnetic Micromanipulator
    (Sage Publications Ltd, 2019-09-09) Boyuk, Mustafa; Eroglu, Yakup; Ablay, Gunyaz; Icoz, Kutay
    Magnetic micromanipulators are capable of generating wide range of magnetic forces to manipulate magnetic microparticles for biomedical applications. In this study, a multipole magnetic micromanipulator system including electromagnets, driver circuitry and control unit is designed, modeled and implemented. The micromanipulator can produce a broad range of magnetic forces up to 25 pN on a single magnetic microparticle (1-10 mu m diameter) that is 5 mm away from the electromagnet core tip. Both linear and nonlinear controllers are designed and implemented, and the proposed nonlinear controller produces smooth control currents to assure closed-loop stability of the system with 1 s non-overshoot transient response and zero steady-state tracking error. The maximum output current of the driver circuitry is set to 1 A. The single particle at the center is moved at a speed of 5 mm/s. The fully automatic system can be utilized in applications related to single cell or microparticle manipulations.
  • Article
    Citation - WoS: 15
    Citation - Scopus: 14
    Effects of Silver Nanowires and Their Surface Modification on Electromagnetic Interference, Transport and Mechanical Properties of an Aerospace Grade Epoxy
    (Sage Publications Ltd, 2024-03-03) Ozkutlu Demirel, Merve; Ozturkmen, Mahide B.; Savas, Muzeyyen; Mutlugun, Evren; Erdem, Talha; Oz, Yahya
    The aerospace industry has progressively grown its use of composites. Electrically conductive nanocomposites are among important modern materials for this sector. We report on a bulk composite containing silver nanowires (AgNW) and an aerospace grade epoxy for use in carbon fiber reinforced polymers (CFRPs). AgNWs' surfaces were also modified to enhance their ability to be dispersed in epoxy. Composites were obtained by use of three-roll milling which is of major interest for industrial applications, especially for the aerospace sector, since the process is scalable and works for aerospace grade resins with high curing temperatures. Our main objective is to improve the electromagnetic interference (EMI) shielding performance of CFRPs via improving the properties of the resin material. The addition of AgNWs did not considerably alter the flexural strength of the epoxy, however the composite with surface-modified AgNWs has a 46 % higher flexural strength. Adding AgNWs over a low threshold concentration of 0.05 wt% significantly enhanced the electrical conductivity. Conductivities above the percolation threshold lie around 102 S/m. At a concentration of 5 wt% AgNW, the EMI shielding efficiency (SE) of epoxy increased from 3.49 to 12.31 dB. Moreover, the thermal stability of the epoxy was unaffected by AgNWs. As a result, it was discovered that (surface modified) AgNWs improved the (multifunctional) capabilities of the aerospace grade epoxy resin which might be used in CFRPs to further enhance properties of composites parts, demonstrating suitability of AgNWs' as a reinforcement material in aerospace applications.