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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14411/18
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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.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: 3Citation - Scopus: 3Nucleon Resonances With Spin 3/2 and Isospin 1/2(Iop Publishing Ltd, 2020-08-04) Azizi, K.; Sarac, Y.; Sundu, H.Investigation of the nucleon's excited states has always become an important research topic because of the rich information they provide. Since their first observation, dating back about 70 years, the investigation of their various parameters contributed both to the development of the quark model and a better understanding of the QCD as the theory of strong interaction. Their investigation still has importance. The research conducted on the nucleon excited states is helpful to probe the missing resonances predicted by the quark model but not observed yet. With this motivation, we study the low lying nucleon resonance with I(J(P)) = 1/2(3/2(-)) and its corresponding orbital and radial excitations with I(J(P)) = 1/2(3/2(+)) and I(J(P)) = 1/2(3/2(-)), respectively. Using the QCD sum rule method, we calculate the masses and pole residues of these states. The obtained mass results are consistent with the mass ranges presented in PDG for the resonances N(1520)(3/2(-)), N(1700)(3/2(-)), and N(1720)(3/2(+)). The results of masses and residues of these states may be used as input parameters to calculate various quantities related to their electromagnetic, weak and strong interactions with other particles with the aim of getting more information on their natures and structures.Article Citation - WoS: 9Citation - Scopus: 9Sr addition and its effect on the melt cleanliness of A356(Iop Publishing Ltd, 2020-02-01) Atakav, Baturalp; Gursoy, Ozen; Erzi, Eray; Tur, Kazim; Dispinar, DeryaStrontium modification of Al-Si alloys has known to have several beneficial effects such as increased feedability, the formation of fibrous Si and increased mechanical properties. However, in the presence of Sr, during melting and holding durations, the oxide structure of the dross may change which leads to several problems during casting operations. In this work, the amount of Sr was changed and the melt was held for 1 h. Reduced Pressure Test (RPT) was used to asses melt quality change and it was found that cleanliness was increased due to the fading of Sr.Conference Object Citation - WoS: 4Citation - Scopus: 4A Material Perspective on Consequence of Deformation Heating During Stamping of Dp Steels(Iop Publishing Ltd, 2017-09) Simsir, C.; Cetin, B.; Efe, M.; Davut, K.; Bayramin, B.Recent studies showed that, during stamping of high strength steels at industrially relevant production rates, local temperature in the blank may rise up to 200 degrees C - 300 degrees C due to deformation heating. Moreover, die temperature may also rise up to 100 degrees C - 150 degrees C for progressive stamping dies. Based on the common assumption that the blank softens as the temperature increases, thermal softening creates a margin in Forming Limit Diagram (FLD) and therefore the FLD determined at room temperature can safely be used for those cases. In this article, the validity of this assumption on DP590 steel is questioned by high temperature tensile tests (RT - 300 degrees C) at various strain rates (10(-3) s(-1) - 1 s(-1)). The results indicated a decrease both in uniform and total elongation in 200 degrees C - 300 degrees C range together with several other symptoms of Dynamic Strain Aging (DSA) at all strain rates. Concurrent with the DSA, the simulated FLD confirms the lower formability at high temperature and strain rates. Thus, it is concluded FLD determined at RT may not be valid for the investigated steels.Article Citation - WoS: 10Citation - Scopus: 10Synthesis and Characterization of Novel High Temperature Structural Adhesives Based on Nadic End Capped Mda-Btda Copolyimide(Iop Publishing Ltd, 2018-08-31) Acar, Oktay; Varis, Serhat; Isik, Tugba; Tirkes, Seha; Demir, Mustafa M.A series of novel copolyimide structural adhesives were synthesized using 4,4'-diaminodiphenyl-methane (MDA), 3,4'-oxydianiline (ODA) and 3,3',4,4'-benzophenonetetracarboxylic acid dianhy-dride (BTDA) as co-monomers, and nadic anhydride as an end cap reagent. The adhesives with different MDA and ODA contents were examined in terms of their structure, thermal stability, mechanical properties, and adhesive performance. They have glass transition temperatures (T-g) about 400 degrees C, with thermal stability up to 500 degrees C. The effect of diamine monomer compositions on adhesion performance and processability of the copolyimides were studied. The copolyimides exhibited adhesion strength up to 16.3 MPa at room temperature. Nadic end capped MDA-BTDA-ODA copolyimide resins gained adjustable and controllable processability with the addition of ether bridged aromatic segments. The copolyimide adhesive with equimolar composition of MDA: ODA is distinguished form the both commercial PMR-15 and LARC RP-46 polyimides in terms of its better processability and mechanical performance.Article Citation - WoS: 13Citation - Scopus: 13Revealing Photoluminescence and Nonlinear Optical Absorption Characteristics of Pbmo<sub>0.75</Sub>w<sub>0.25< Single Crystal for Optical Limiting Applications(Iop Publishing Ltd, 2024-04-18) Dogan, Anil; Karatay, Ahmet; Isik, Mehmet; Yildiz, Elif Akhuseyin; Gasanly, Nizami; Elmali, AyhanNonlinear absorption properties of PbMo0.75W0.25O4 single crystal fabricated by the Czochralski method were studied. The band gap energy of the crystal was determined as 3.12 eV. Urbach energy which represents the defect states inside the band gap was found to be 0.106 eV. PbMo0.75W0.25O4 single crystal has a broad photoluminescence emission band between 376 and 700 nm, with the highest emission intensity occurring at 486 nm and the lowest intensity peak at 547 nm, depending on the defect states. Femtosecond transient absorption measurements reveal that the lifetime of localized defect states is found to be higher than the 4 ns pulse duration. Open aperture (OA) Z-scan results demonstrate that the PbMo0.75W0.25O4 single crystal exhibits nonlinear absorption (NA) that includes two-photon absorption (TPA) as the dominant mechanism at the 532 nm excitations corresponding to 2.32 eV energy. NA coefficient (beta(eff)) increased from 7.24 x 10(-10) m W-1 to 8.81 x 10(-10) m W-1 with increasing pump intensity. At higher intensities beta(eff) tends to decrease with intensity increase. This decrease is an indication that saturable absorption (SA) occurred along with the TPA, called saturation of TPA. The lifetime of the defect states was measured by femtosecond transient absorption spectroscopy. Saturable absorption behavior was observed due to the long lifetime of the localized defect states. Closed aperture (CA) Z-scan trace shows the sign of a nonlinear refractive index. The optical limiting threshold of PbMo0.75W0.25O4 single crystal at the lowest intensity was determined as 3.45 mJ/cm(2). Results show that the PbMo0.75W0.25O4 single crystal can be a suitable semiconductor material for optical limiting applications in the visible region.Article Citation - WoS: 8Citation - Scopus: 7Tunable Nonlinear Absorption and Optical Limiting Behavior of Nabi(mo<sub>x</Sub>w<sub>1-x< Single Crystals With Ratio of Molybdenum/Tungsten(Iop Publishing Ltd, 2023-06-14) Pepe, Yasemin; Yildiz, Elif Akhuseyin; Isik, Mehmet; Karatay, Ahmet; Gasanly, Nizami; Elmali, AyhanThe compositional effect of Mo/W ratio on linear, nonlinear absorption and optical limiting behavior of the NaBi(MoxW1-xO4)(2) single crystals grown by Czochralski technique was investigated. X-ray diffraction patterns of the studied crystals presented well-defined peaks associated with the tetragonal crystalline structure. The nonlinear absorption performance and optical limiting threshold were determined using an open-aperture Z-scan technique. A theoretical model including one photon absorption (OPA), two photon absorption (TPA) and free carrier absorption was used to determine the nonlinear absorption parameters. All of the results showed that defect states, which strongly affect nonlinear absorption (NA) and optical limiting behaviors, can be tuned with the Mo/W ratio, enabling NaBi(MoxW1-xO4)(2) single crystals to be used in desired optoelectronic applications. Linear optical absorption analysis revealed that bandgap energy and defect states can be tuned by changing the Mo/W ratio in the crystal structure. The obtained results showed that all the studied crystals had NA behavior and the nonlinear absorption coefficient decreased with increasing Mo/W ratio. Sequential TPA is the main NA mechanism for these crystals due to the fact that the incident light energy is lower than the bandgap energies and the existence of the real intermediate state around 2.32 eV.