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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14411/18
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Article Citation - WoS: 5Citation - Scopus: 54D Printing of Reusable Mechanical Metamaterial Energy Absorber, Experimental and Numerical Investigation(Iop Publishing Ltd, 2025-06-01) Fallah, Ali; Saleem, Qandeel; Scalet, Giulia; Koc, BahattinThis study investigates the compression behavior, energy absorption, shape memory properties, and reusability of 4D-printed smart mechanical metamaterials. Four structural configurations, i.e. honeycomb, re-entrant, and two modified re-entrant designs were developed to assess microstructure effects. Samples were fabricated using Polylactic Acid (PLA), a widely used shape memory polymer (SMP) in 4D printing, and polyethylene terephthalate glycol (PETG), an emerging SMP with demonstrated shape memory performance in recent studies. Cold-programming-induced shape recovery was evaluated at room temperature, simulating real-world conditions. Finite element simulations of compression and shape memory cycles matched experimental results well. Auxetic samples with negative Poisson's ratios showed superior energy absorption. However, only PETG demonstrated sufficient reusability, while PLA proved unsuitable for reusable designs. The PETG-3 modified re-entrant structure exhibited the best performance, with high energy absorption, delayed densification onset, and shape recovery and reusability factors of 0.95 and 0.96, respectively. Findings highlight the importance of considering both shape recovery and reusability when designing smart structures to address industrial challenges.Article Citation - WoS: 2Citation - Scopus: 1Integrating Theoretical and Experimental Approaches To Unveil the Mechanical Properties of Cusbse<sub>2</Sub> Thin Films(Iop Publishing Ltd, 2024-11-21) Surucu, Ozge; Gencer, Aysenur; Usanmaz, Demet; Parlak, Mehmet; Surucu, GokhanAn exhaustive investigation of the mechanical characteristics of CuSbSe2 thin films is conducted in this study by combining experimental nanoindentation methods with theoretical simulations. The Ab-initio Molecular Dynamics (AIMD) calculations are performed with the machine learning (ML) force fields. By employing the Vienna Ab-initio Simulation Package (VASP) based on Density Functional Theory (DFT), theoretical inquiries are carried out to identify crucial parameters, such as bonding characteristics, elastic constants, hardness, bulk modulus, shear modulus, Young's modulus, and Poisson's ratio. Experimental validation is conducted using nanoindentation to investigate load-dependent hardness and Young's modulus in a manner that closely matches the theorized predictions. The anomalies between experimental and theoretical outcomes are ascribed to anisotropic behavior and grain boundaries. Furthermore, an investigation is conducted into the directional dependence of sound wave velocities in the CuSbSe2 films, leading to the revelation of intricate elastic property details. By employing an integrated theoretical-experimental approach, the present attempt not only increases the knowledge concerning CuSbSe2 films but also fortifies the relationship between theory and experiment, thereby bolstering the dependability of our results. The insights provided as a result of this paper facilitate the development of CuSbSe2 film applications in a variety of technological fields in the future.Article Citation - WoS: 3Citation - Scopus: 3Performance Enhancement of Silicon Photodiodes Through the Integration of Green Synthesized Reduced Graphene Oxide Variants(Iop Publishing Ltd, 2024-08-06) Yildiz, D. E.; Sürücü, Özge; Surucu, O.; Balaban, H. Mert; Bilici, I; Yildirim, M.; Sürücü, Özge; Mert Balaban, H.; Electrical-Electronics Engineering; Electrical-Electronics EngineeringThis study examines the potential of enhancing the optoelectronic properties of silicon photodiodes by producing and analyzing heterostructures that incorporate reduced graphene oxide (rGO) synthesized with silicon using different reduction methods. Graphene oxide (GO) was manufactured utilizing an enhanced Hummers' method. Subsequently, reduced graphene oxides (rGOs) were made by chemical and thermal reduction processes, which are considered ecologically friendly. The use of ascorbic acid to produce ascorbic acid-reduced graphene oxide (ArGO) and thermal processing to produce thermally reduced graphene oxide (TrGO) have significantly contributed to the development of high-performance photodiode technology. The electrical properties were carefully assessed under different levels of light, revealing the substantial impact of integrating reduced graphene oxides (rGOs) on the performance of the diodes. Comparing ArGO/Si, TrGO/Si, and GO/Si heterostructures shows that customized rGO has the potential to greatly influence the responsivity and efficiency of Si-based optoelectronic devices, making a significant contribution to photodiode technology.Article Citation - WoS: 33Citation - Scopus: 36Mechanical, Thermo-Mechanical and Morphological Characterization of Abs Based Composites Loaded With Perlite Mineral(Iop Publishing Ltd, 2019-11-18) Alghadi, Aiah Mohamed; Tirkes, Seha; Tayfun, UmitAcrylonitrile-butadiene-styrene (ABS) copolymer was filled with perlite mineral (PER) at four different loading level of 2.5%, 5%, 10% and 15%. ABS/PER composites were produced using lab-scale micro-compounder followed by injection molding process. Mechanical, thermo-mechanical, melt-flow and morphological properties of composites were reported by tensile and impact tests, dynamic mechanical analysis (DMA), melt flow index (MFI) test and scanning electron microscopy (SEM), respectively. Mechanical characterizations revealed that tensile strength, elongation and Youngs? modulus of ABS were improved by PER inclusions. However, impact strength of ABS reduced with increase of PER concentration. Glass transition temperature of ABS displayed increasing trend for %5 concentration of PER. MFI test implied that PER addition caused slight decreasing for MFI value of unfilled ABS. Homogeneous dispersion of PER particles into ABS matrix for their lower loading level was obtained from SEM micrographs of composites. According to findings, 5% PER containing sample exhibited the best performance and it was remarked as the most suitable candidate among fabricated ABS based composites.Article Citation - Scopus: 1Samarium and Yttrium Doping Induced Phase Transitions and Their Effects on the Structural, Optical and Electrical Properties of Nd<sub>2</Sub>sn<sub>2< Ceramics(Iop Publishing Ltd, 2020-01-15) Saleh, Adli A.; Qasrawi, A. F.; Hamamera, Hanan Z.; Khanfar, Hazem K.; Yumusak, G.In this work, the effects of Sm+3 and Y+3 doping onto the structural, optical and electrical properties of Nd2Sn2O7 are investigated. An atomic content of 3.49% and 4.29% of Sm and Y, respectively, were sufficient to alter the physical properties of the Nd2Sn2O7. Particularly, the Y+3 ionic substitution decreased the lattice constant, narrows the energy band gap, changed the conductivity type from n- to p- type and increased the electrical conductivity by 73 times without changing the cubic nature of structure of the pyrochlore ceramics. On the other hand, Sm+3 ionic substitutions changed the cubic structure to hexagonal or trigonal and forced optical transitions in the infrared range of light. The energy band gap shrunk from 3.40 to 1.40 eV, the defect density is reduced and the electrical conductivity increased by 47 times via Sm doping. These doping agents' makes the neodymium stannate pyrochlore ceramics more appropriates for optoelectronic applications.Article Citation - WoS: 2Citation - Scopus: 2Post Annealing Effects on the Structural and Optical Properties of Moo<sub>3</Sub> Sandwiched With Indium Slabs(Iop Publishing Ltd, 2019-11-08) Qasrawi, A. F.; Qasrawı, Atef Fayez Hasan; Kmail, Haifaa K.; AbuSaa, M.; Khanfar, Hazem K.; Qasrawı, Atef Fayez Hasan; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringMolybdenum trioxide thin films are prepared by the thermal evaporation technique under vacuum pressure of 10(-5) mbar through insertion of indium slabs of thickness of 200 nm between layers of MoO3 and annealing the produced films in the air atmosphere at 250 degrees C for one hour. The films are studied by means of x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, and optical spectrophotometry techniques. The structure of the films is found to be composed monoclinic MoO3, tetragonal indium and cubic In2O3. The phase percentage of In2O3 in the films increased to 26.3% upon annealing at 250 degrees C. The annealing process increased the microstrain, the defect density, the oxygen atomic content and lowered the crystallites and grains sizes in the films. Optically, two energy band gaps of values of 3.20 and 1.70 eV were detected for the MoO3/In/MoO3 system. In addition, nonlinear dielectric response associated with wide range of tunability in the dielectric constant value, in the optical conductivity and in the terahertz cutoff frequency was observed in the near IR spectral range. The annealing of the samples improved the nonlinearity in these parameters and make MoO3/In/MoO3 system more appropriates for optoelectronic technology applications as terahertz cavities and frequency convertors.Conference Object Reflections of Memory Boom on the Architectural Researches in Turkey(Iop Publishing Ltd, 2020-12-10) Cihangiroglu, Melike SelcanMemory is a notion studied by many different disciplines with its various points of views. Researchers, who examine memory and its sub-categories, discuss this notion through interactions of people within their individual; societal; cultural; and urban contexts. It is possible to observe a considerable increase of researches on the phenomenon of memory in the last two decades. These research increase is labelled in the literature as 'memory-boom'. The term "memory-boom" could be explained as the importance and attention given to the notion of memory in society and the academic world. An example of this 'memory-boom' can be seen in the increasing number of researches after the World War II and then The Holocaust. A similar rise was experienced after the 9/11 World Trade Centre attack. As a result of these incidents, which had a worldwide impact on masses, reasons behind memory-boom started to emerge in some researches. In this study, 'memory-boom' is discussed within the national context of Turkey. Notion of memory has been studied in many researches in Turkey, as in the literature of elsewhere. This study focuses on the rise of academic works in Turkey that examine relations between architectural buildings and memory within the field of architecture, as opposed to researches focusing solely on the concept of memory. The purposes of the study could be explained as twofold: 1) to understand reasons behind the increase of memory researches in Turkey and triggers or reasons that may be affecting these works, 2) to understand reasons of the memory-boom related to architecture and architectural buildings in Turkey. In this context, this study is constructed as a preliminary work, which has limited research universe that encompass academic dissertations in architecture and interior design disciplines, written between years of 2000-2020 in Turkey. Thesis, which are archived at the "Council of Higher Education National Thesis Center" database, are examined within the scope of this study, to be able to demonstrate the relations between architecture and memory-boom. The study has a qualitative, interpretive conceptual framework and it relies on critical readings of the existing literature as a method. It is aimed to understand notable similarities and/or differences between triggering reasons of memory-boom in Turkey and related architectural studies. The study intends to contribute to the literature by drawing attention to the notion of "memory-boom" in national literature and to expand its place in academic works and researches.Conference Object Developments in Technology-Based Courses Contents of Interior Architecture Departments in Turkey(Iop Publishing Ltd, 2020-12-01) Aykac, Gokce NurThe introduction of information technologies in space design disciplines begins with the use of the Computer Aided Design concept in those disciplines. Since the first example of CAD tool which was launched in 1963, the ability to design using computers has been a method adopted by architecture and space design disciplines and transferred to the educational context. There were changes and transformations in this method due to the needs created by the developing building technologies. The CAD technology, has been adopted to the space design education in order to support the courses. The CAD which was created for challenging the difficulties in the practicing area and speeding up the process, also takes place among the traditional methods of space design in the Interior Architecture discipline. The possibilities provided by those digitally created spatial mediums, have led to a rotational improvement in both education and practice. In addition, the reflections of technological developments in the social context in last decade on many areas of life have led to the necessity of reorganizing the educational contents. Academic studies conducted in recent years, are designed to include the last technological developments in today's educational contents and to reflect students' interests and commitment to these technologies in direct proportion. Bearing this in mind, the objective of this study is to read out the reflection of the developments mentioned above on the Interior Architecture discipline in Turkey by monitoring the developments in the context of the need of updating the educational contents. In order to meet the social developments and today's skills, space design education must follow the technological context in parallel. Based on these considerations, the studies of Turkey which were examined in this research have been conducted before could be explained as inadequate. In this context, to examine the curriculum of the Interior Architecture departments of Turkey and to monitor the updates mentioned before constitute the main focus of the study. CAD-based courses in the curriculum of the Interior Architecture departments were determined and the contents were examined. These analyses were achieved in the context of the methods, techniques and tools used in the courses, and after, the situation of the information based courses were determined. It was concluded that these courses were transformed in direct proportion in line with the increasing needs in the educational context with the developing technology and updates should continue in the context of meeting today's skills.Article Citation - WoS: 4Citation - Scopus: 5Znse/Al Nanosandwiched Structures as Dual Terahertz-Gigahertz Signal Receivers(Iop Publishing Ltd, 2019-03-20) Qasrawi, A. F.; Alsabe, Ansam M.In the current work, we focus on the enhancements in performance of the ZnSe terahertz/gigahertz signal receivers which are achieved by the insertion of nanosheets of Al layers of thickness of 30 nm between two 500 nm thick layers of ZnSe. The Al nanosandwiching which decreased the defect density, stacking faults and increased the grain size in the films increased the optical conductivity by more than 125%, increased the drift mobility to 313 cm(2) V-1 s(-1) and widens the plasmon frequency ranges to 0.49-4.92 GHz. In addition, the analysis of the terahertz cutoff (f(co)) frequency spectra have shown that the presence of Al nanosheets improves the cutoff frequency value by three orders of magnitude making the ZnSe receivers more suitable for visible light and IR communication technology. The value of f(co) is 49.6 THz when light signal of wavelengths of 408 nm that suits blue lasers is irradiated. Moreover, the impedance spectroscopy analysis in the gigahertz frequency domain has shown that the Al sandwiched ZnSe exhibits negative capacitance spectra in the frequency domain of 0.01-1.04 GHz. This property is useful for parasitic capacitance cancelling and noise reducing in circuits. Furthermore, the study of the microwave cutoff frequency spectra has shown that the value of f(co) is enhanced by three orders of magnitude above 1.5 GHz.Article Citation - WoS: 26Citation - Scopus: 27Preparation of Electrospun Pcl-Based Scaffolds by Mono/Multi-functionalized Go(Iop Publishing Ltd, 2019-05-28) Basar, Ahmet Ozan; Sadhu, Veera; Sasmazel, Hilal Turkoglu; Turkoglu Sasmazel, HilalIn the present study, sythetic biodegradable polymer poly(epsilon-caprolactone) (PCL) and graphene oxide (GO) were combined together to prepare 3D, composite tissue scaffolds (PCL/GO scaffolds) by using electrospinning technique. Also, the influence of Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) and/or thiophene (Th) modified GO on the composite PCL/GO mats (PCL/GO, PCL/GO-GRGDSP, PCL/ GO-Th, PCL/GO-GRGDSP-Th) was further investigated. Characteristic examinations of the scaffolds were carried out by scanning electron microscope (SEM), contact angle (CA) measurements, x-ray photoelectron spectroscopy, TGA, electrical conductivity tests, phosphate buffer saline absorption and shrinkage tests and mechanical tests. All of the scaffolds were exhibited suitable bead free and uniform morphology according to SEM images. With the addition of GO, better hydrophilicity and a slight CA decrease (similar to 5 degrees) for the PCL/GO scaffolds were observed. Mechanical properties were reinforced drastically with the addition and well-dispersion of GO into PCL matrix. The incorporation of PCL and GO exhibited enhanced electrical conductivity and the highest value was found for PCL/GO-GRGDSP-Th (2%) as 15.06 mu S cm(-1). The MG-63 osteoblast cell culture studies (MTT assay, ALP activity, Alizarin-Red staining, fluorescence and SEM analyses) showed that PCL/GO-GRGDSP-Th (1%) scaffolds exhibited the highest biocompatibility performance (1.87 fold MTT absorbance value comparing with neat PCL) due to the advanced properties of GO and the biological interfaces.