Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 2Citation - Scopus: 1Toward Cost-Effective and Lightweight Doppler Radars: Papercraft-Based Components and Comparisons With Aluminum and 3-D Printed Alternatives(Institute of Electrical and Electronics Engineers Inc., 2024) Karatay,A.; Atac,E.; Yaman,F.Doppler radar systems have an essential role in various applications, including aviation, weather forecasting, and military surveillance. However, their high fabrication costs and heavy weight may limit their utilization in rapid prototyping, small-scale applications, and seamless transportation. To address these challenges, a novel papercraft-based approach for producing the entire Doppler radar system's horn antenna, hybrid tee, and short termination components in the X-band was investigated with details in this study, alongside conventional aluminum and 3-D printing methods. This article presents the first attempt to develop a Doppler radar using papercraft-based manufacturing. The papercraft-based approach is cost-effective, lightweight, flexible, and readily available, offering a promising route for improving and fabricating Doppler radar systems that are both affordable and accessible, particularly in resource-limited settings. The experimental results show that the papercraft-based components can perform comparably to conventional aluminum-based and 3-D-printed components, making it an innovative and cost-effective solution for fabricating Doppler radar systems. © 2023 IEEE.Article Citation - WoS: 3Citation - Scopus: 3Liquid Metal-Tunable Miniaturized Bimodal Cavity for Enhanced Measurement Accuracy in the Ism Bands(Ieee-inst Electrical Electronics Engineers inc, 2024) Karatay, Anil; Yaman, FatihEnhancing measurement accuracy or reducing the effect of the neighboring modes in resonant cavities may necessitate the separation of mode frequencies. However, in ISM-band measurement configurations utilizing a rectangular or cylindrical cavity, the placement of the first two modes at 2.45 and 5.8 GHz is unattainable, necessitating the presence of additional modes in between that would potentially degrade measurement accuracy. This article begins with an analytical approach, employing Lagrange multipliers for the first time to reveal the level of separation achievable in the frequency domain between the initial two modes within these types of conventional cavities. The analytical results were also verified with a numerical grid search. Subsequently, innovative strategies have been introduced to surpass this intrinsic constraint that reduces the measurement accuracy in various applications. A novel miniaturized cavity configuration has been proposed to operate bimodally at 2.45 and 5.8 GHz and manufactured with a 3-D printer. It has been ensured that there are no physical modes present in between, and measurements of the structure have been conducted. Another notable innovation of the article is the capability of tuning the proposed cavity structure by means of liquid metal displacement. Thus, a more flexible tuning method compared to mechanical tuning techniques can be achieved, enabling precise adjustment of the desired measurement frequency. Good agreement between the simulation and measurement results has been reported.Article Citation - WoS: 17Citation - Scopus: 19Development of Ca(oh)2-Based Geopolymer for Additive Manufacturing Using Construction Wastes and Nanomaterials(Elsevier, 2023) Mortada, Youssef; Masad, Eyad; Kogbara, Reginald B.; Mansoor, Bilal; Seers, Thomas; Hammoud, Ahmad; Karaki, AymanRecent growth in additive manufacturing (AM) or 3D printing in the construction field has motivated the development of various materials that vary in its composition and properties. This paper introduces, characterizes, and evaluates the performance of a sustainable and environmentally friendly geopolymer mixture composed of construction wastes. The geopolymer mixture has calcium hydroxide (Ca(OH)2) as the main alkaline activator and incorporates nanomaterials such as nano-silica and nano-clay to enhance its suitability for AM. The combined use of Ca(OH)2 for alkali activation, and nanomaterials for tailoring the behavior of construction wastes for 3D printing, is novel and addresses the shortcomings of conventional alkaline activators. The paper includes the outcomes of the analysis of the mechanical properties, printability, and microstructure of the geopolymer mixture. The 28-day compressive strength of the mixture reached 42 MPa with ambient temperature curing, which is comparable to traditional geopolymers. The inclusion of 1 wt % of nano-silica accelerated the geopolymerization process and led to the largest (35 %) reduction in the setting time. Similarly, incorporating 1 wt % of nano-clay led to reduction of the thermal conductivity from 0.709 W/mK to 0.505 W/mK, due to the introduction of thermal barriers. The printability of the studied waste-based geopolymer mixture was validated through the successful fabrication of a 3D-printed model. © 2023 The AuthorsArticle Citation - WoS: 39Citation - Scopus: 41Effect of Post Fabrication Aging Treatment on the Microstructure, Crystallographic Texture and Elevated Temperature Mechanical Properties of In718 Alloy Fabricated by Selective Laser Melting(Elsevier, 2022) Özer, Seren; Bilgin, Güney Mert; Davut, Kemal; Esen, Ziya; Dericioğlu, Arcan.FThe effect of building direction and post fabrication aging treatment on the microstructure, crystallographic texture and high temperature mechanical properties of Inconel 718 (IN718) alloy fabricated by selective laser melting (SLM) method was investigated. After aging, arc-shaped structures seen in as-fabricated samples disappeared and converted into a mixture of columnar and equiaxed grains. Nano-sized γ″ and/or γ′ precipitates were formed upon aging; however, MC type carbides and Laves phase encountered in as-fabricated samples were not dissolved completely after aging. Moreover, aging did not alter the texture ((001)//building direction (BD)) of as-fabricated samples. Mechanical properties of the alloys under tension were influenced by the build direction, aging time and test temperature. As-fabricated samples produced in vertical direction exhibited higher room temperature strengths with lower ductility due to orientation of overlapped prior melt pools. Room temperature tensile test results revealed that peak aging caused a significant improvement in ultimate tensile strength (UTS), from 1066.5 MPa and 998.4 MPa to 1408.5 MPa and 1330.4 MPa whereas elongation values decreased from 27.5% and 32.2% to 19.6% and 23.7% in vertically and horizontally built samples, respectively. Peak-aged samples (aged at 700 °C for 8 h) tested at 600 °C displayed serrated regions in their stress-strain curves due to dynamic strain aging (DSA). Although strength values of the samples displayed an expected decrease by temperature, ductility of the samples reduced to minimum at temperatures around 700–800 °C, which was attributed to intermediate temperature embrittlement.Article Citation - WoS: 19Citation - Scopus: 21Synthesis and Additive Manufacturing of Calcium Silicate Hydrate Scaffolds(Elsevier, 2021) Oğur, Ezgi; Botti, Renata; Bortolotti, Mauro; Colombo, Paolo; Ahmetoğlu, Çekdar VakıfA Calcium silicate hydrate (CSH) powder containing above 60 wt% xonotlite (remaining being tobermorite, scawtite and calcite) were produced from lime and ordinary recycled soda-lime glass via simple hydrothermal synthesis route. The thermogravimetric analysis demonstrated only similar to 20%weight loss up to 800 degrees C (at about the transformation temperature of CSHs to wollastonite), reaching a plateau in the 800-1200 degrees C temperature range. The synthesized CSH powder was employed for the fabrication of both green and heat-treated scaffolds by additive manufacturing (AM), possessing a high porosity (>80 vol%) and limited strength (similar to 0.9 MPa). (c) 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).