TR-Dizin İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/396
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Article Citation - Scopus: 1Kayseri İlindeki Bazı Tarihi Eserlerde Bozunma Etkilerinin Tahribatsız Deney Yöntemleriyle Değerlendirilmesi(TMMOB Chamber of Geological Engineers, 2025-06-11) Akin, Mutluhan; Akin, Muge; Akgül, Muhammed Kamilİç Anadolu’da önemli bir yerleşim merkezi olan Kayseri, farklı dönemlerden günümüze kadar gelen birçok tarihi esere ev sahipliği yapmaktadır. İlin farklı bölgelerinde özellikle yoğun yerleşimin bulunduğu alanlarda, Selçuklu Dönemi’ne ait 12. ve 14. yüzyıllar arası yapılmış çok sayıda cami, kümbet ve medrese türü tarihi esere rastlamak mümkündür. Kültürel miras niteliğindeki bu eserler çoğunlukla yakın çevrede yoğun olarak bulunan farklı renk ve dokudaki ignimbirit türü kaya malzemesi kullanılarak inşa edilmişlerdir. Genel olarak düşük dayanıma sahip ve su etkilerine karşı hassas olan bu ignimbiritler zaman içerisinde atmosferik etkenler, hava kirliği, vandalizm vb. gibi olaylar sonucunda bozunmakta ve ilksel özelliklerini kaybetmektedirler. Bu çalışmada Kayseri il merkezindeki Roma ve Selçuklu dönemlerine ait tarihi eserler ile bu eserlerde zaman içinde meydana gelen bozunma etkileri incelenmiştir. Bozunma etkilerinin gözlemsel olarak incelenmesinin yanı sıra, eserlere herhangi bir zararı bulunmayan tahribatsız deney yöntemlerinden İğne Penetrometresi, Schmidt Çekici ve P-dalga hızı deneylerinden faydalanılmıştır. Bunun yanı sıra, bozunmuş ignimbirit bloklarına ait yerinde deneylerle belirlenen değerler, aynı malzemeye ait taze örneklerin fiziko-mekanik özellikleri ile karşılaştırılmıştır. Yapılan değerlendirmeler sonucunda tarihi eserlerin taban bölümlerinde özellikle kılcallık sebebiyle pullanma ve kavlaklanma türü bozunmaların geliştiği ve ignimbiritlerin bu bölümlerde dayanımlarını önemli ölçüde kaybettiği tespit edilmiştir. İncelenen kümbetlerin bazılarına uygulanan iyileştirme çalışmalarında ise kümbetlerin çevresinde bulunan yüzey suyu drenajlarının yeterli ölçüde yapılamadığı ve yağmur ile biriken suların tarihi eserlerin daha fazla bozunmasına sebep olduğu saptanmıştır. Kültürel miras olarak değerlendirilen bu tarihi yapıların korunup gelecek nesillere aktarılması amacıyla, ignimbirit yapılarının yüzeysularına karşı duyarlılığı dikkate alınarak tarihi kümbetlerin çevresinde su drenajı iyileştirme çalışmaları yapılması önerilmektedir.Article Thermal Stresses in SOFC Stacks: The Role of Mismatch Among Thermal Conductivity of Adjacent Components(Tubitak Scientific & Technological Research Council Turkey, 2021-06-30) Aydin, Ozgur; Matsumoto, Go; Shiratori, YusukeGenerating power from renewable biogas in solid oxide fuel cells (SOFCs) is an environment-friendly, efficient, and promising energy conversion process. Biogas can be used in SOFCs via a reforming process for which dry reforming is more suitable as the reforming agent exists in the biogas mixture. Biogas can be directly reformed to H-2 -rich fuel stream in the anode chamber of a SOFC by the heat released during power generation. Exploiting the heat and water produced in the SOFC for internal reforming of biogas makes the energy conversion process very efficient; however, various challenges are reported. Thus, indirect internal reforming is opted for which a separate reforming domain is required. In an indirect internal reformer operating at usual conditions, dry reforming rate is quite high in the inlet and it decreases steeply toward the fuel outlet. Great temperature gradients develop over the reformer, since the dry reforming reaction is strongly endothermic. The abruptly varying rate of the reforming reaction affects the temperature fields in the adjacent components of SOFC and hence intolerable thermal stresses emerge on the SOFC components. In our preceding study, we graded the reforming domain, homogenized the temperature profile over the reforming domain, and executed performance and durability experiments. However, most of the experiments failed due to fracturing SOFC components hinting at existence of thermal stresses. In that study, we focused on minimizing the temperature gradients within the reforming domain; namely, we neglected the other processes. To eliminate the thermal stresses, we modeled the entire module of SOFC equipped with a reformer featuring a graded reforming domain. We found that the mismatch between the thermal conductivities of the adjacent module components is the major reason for the thermal stresses. When the mismatch is eliminated, thermal stresses disappear even if the reforming domain is not graded.Article Tax Compliance Behaviour and Lab Experiments: A Literature Review(Maliye Bakanligi, 2021) Demirtas, Burak KaganThe purpose of this article is to conduct a literature review of the papers based on laboratory experiments to analyze tax evasion behaviors of individuals. Although experimental studies in economics have become more and more important day by day, there are almost no publications on experimental economics in the Turkish literature. The studies are examined especially in terms of experimental designs because this study also aims to increase awareness about laboratory experiments. This review also discusses the criticism of laboratory experiments and concludes that the results obtained from laboratory experiments are important and it would be beneficial to support them with field experiments.Article Optimizing Parameters for Efficient Computation With Fully Homomorphic Encryption Schemes(Tubitak Scientific & Technological Research Council Turkey, 2025-03-21) Karaagac, Cavidan Yakupoglu; Rohloff, Kurt; Yakupoğlu Karaağaç, Cavidan; Yakupoglu, CavidanIn this study, we aim to provide a parameter selection approach for the BFVrns scheme, one of the prominent fully homomorphic encryption (FHE) schemes. Selecting parameters for lattice-based FHE schemes poses a practical challenge for both experts and nonexperts. To solve this problem, we introduce a hybrid approach that combines theoretical approach with experimental analysis. First, we employ regression analysis to examine the impact of parameters on both performance and security. The varying behavior of FHE parameters in terms of performance, security, and ciphertext expansion factor (CEF) makes parameter selection more challenging. To address this issue, we employ a multi-objective optimization algorithm to determine the optimal parameter set for performance, CEF, and security simultaneously. As a result of this optimization, we obtain an improved parameter set that enhances performance at a given security level while ensuring correctness and resistance to lattice-based attacks, maintaining at least 128-bit security. Our results achieve an average similar to 5x reduction in CEF and generally better performance compared to the parameter sets in a previous BFVrns study. Our approach serves as a semi-automated parameter selection method for the PALISADE homomorphic encryption library, a widely recognized FHE library. This study sets a precedent for other FHE libraries.Article Citation - WoS: 4Citation - Scopus: 5Noise-Assisted Multivariate Empirical Mode Decomposition Based Emotion Recognition(Istanbul Univ-Cerrahapasa, 2018-08-03) Ozel, Pinar; Akan, Aydin; Yilmaz, BulentEmotion state detection or emotion recognition cuts across different disciplines because of the many parameters that embrace the brain's complex neural structure, signal processing methods, and pattern recognition algorithms. Currently, in addition to classical time-frequency methods, emotional state data have been processed via data-driven methods such as empirical mode decomposition (EMD). Despite its various benefits, EMD has several drawbacks: it is intended for univariate data; it is prone to mode mixing; and the number of local extrema must be enough before the EMD process can begin. To overcome these problems, this study employs a multivariate EMD and its noise-assisted version in the emotional state classification of electroencephalogram signals. Emotion state detection or emotion recognition cuts across different disciplines because of the many parameters that embrace the brain's complex neural structure, signal processing methods, and pattern recognition algorithms. Currently, in addition to classical time-frequency methods, emotional state data have been processed via data-driven methods such as empirical mode decomposition (EMD). Despite its various benefits, EMD has several drawbacks: it is intended for univariate data; it is prone to mode mixing; and the number of local extrema must be enough before the EMD process can begin. To overcome these problems, this study employs a multivariate EMD and its noise-assisted version in the emotional state classification of electroencephalogram signals.Article Effects of Dry Particle Coating With Nano-and Microparticles on Early Compressive Strength of Portland Cement Pastes(Tulpar Academic Publishing, 2021-12-16) Yorulmaz, Hediye; Özuzun, Sümeyye; Uzal, Burak; İLkentapar, Serhan; Durak, Uğur; Karahan, Okan; Atis, C. D.It is known that nano-and microparticles have been very popular in recent years since their advantages. However, due to the very small size of such materials, they have very high tendency to agglomeration particularly for nanoparticles. Therefore, it is critical that they are properly distributed in the system to which they are added. This paper investigated the effects of dry particle coating with nano-and microparticles to solve the agglomeration problem. For a clear evaluation, paste samples were preferred to detemine the compressive strength. Nano-SiO<inf>2</inf> and nano-CaCO<inf>3</inf>, microCaCO<inf>3</inf> and micro-SiO<inf>2</inf>, also known as silica fume, were selected as particulate additives. It was studied by the addition of various percentages (0.3, 0.7, 1, 2, 3 and 5%) of nano-and microparticles in cementitious systems, replacing cement by weight with and without dry particle coating. Dry particle coating was made by using a highspeed paddle mixer. Portland cement and additive particles were mixed at 1500 rpm for 30 seconds in high-speed powder mixer designed for this purpose. The 3-day compressive strength of the cement-based samples to which particles were added at the specified rates was determined and the effect of the dry particle coating on the early strength was investigated. According to the results, it was observed that the production of paste with the dry particle coating technique gave higher compressive strength compared to the production of paste directly in early period. Especially with dry particle coating, compressive strength increased more than 100% in paste samples containing 0.3% nano-SiO<inf>2</inf> compared to direct addition without coating. © 2024 Elsevier B.V., All rights reserved.Article Citation - WoS: 2Citation - Scopus: 2Analysis of Optical Gyroscopes With Vertically Stacked Ring Resonators(Tubitak Scientific & Technological Research Council Turkey, 2021-05-31) Hah, DooyoungWithout any moving part, optical gyroscopes exhibit superior reliability and accuracy in comparison to mechanical sensors. Microring-resonator-based optical gyroscopes emerged as alternatives for bulky conventional Sagnac interferometer sensors, especially attractive for applications with limited footprints. Previously, it has been reported that planar incorporation of multiple resonators does not bring about improvement in sensitivity for a given area because the increase in Sagnac phase accumulation does not outrun the increase of area. Therefore, it was naturally suggested to consider vertical stacking of ring resonators because then, the resonators can share the same footprint. In this work, sensitivity performances of such configurations with vertically stacked microring resonators are analyzed and compared to that of a basic (single-resonator) configuration. Through comprehensive study, it is learned that the sensitivity performance of the devices with vertically-stacked resonators (either with a single bus waveguide or with two bus waveguides) does not exceed that of the basic sensor device (single resonator with one bus waveguide), i.e. the basic structure is yet to be remained as the most efficient configuration.Article Citation - WoS: 2Citation - Scopus: 3An Asymptotic-Numerical Hybrid Method for Singularly Perturbed System of Two-Point Reaction-Diffusion Boundary-Value Problems(Tubitak Scientific & Technological Research Council Turkey, 2019-01-18) Cengizci, Suleyman; Natesan, Srinivasan; Atay, Mehmet TankThis article focuses on the numerical approximate solution of singularly perturbed systems of second-order reaction-diffusion two-point boundary-value problems for ordinary differential equations. To handle these types of problems, a numerical-asymptotic hybrid method has been used. In this hybrid approach, an efficient asymptotic method, the so-called successive complementary expansion method (SCEM) is employed first, and then a numerical method based on finite differences is applied to approximate the solution of corresponding singularly perturbed reaction-diffusion systems. Two illustrative examples are provided to demonstrate the efficiency, robustness, and easy applicability of the present method with convergence properties.Article Citation - WoS: 4Citation - Scopus: 4All-Polymer Ultrasonic Transducer Design for an Intravascular Ultrasonography Application(Tubitak Scientific & Technological Research Council Turkey, 2019-07-26) Hah, DooyoungIntravascular ultrasonography (IVUS), a medical imaging modality, is used to obtain cross-sectional views of blood vessels from inside. In IVUS, transducers are brought to the proximity of the imaging targets so that high-resolution images can be obtained at high frequency without much concern of signal attenuation. To eliminate mechanical rotation rendered in conventional IVUS, it is proposed to manufacture a transducer array on a flexible substrate and wrap it around a cylindrical frame. The transducer of consideration is a capacitive micromachined ultrasonic transducer (CMUT). The whole device needs to be made out of polymers to be able to endure a high degree of bending (radius: 1 mm) Bending of the devices leads to considerable changes in the device characteristics, including resonant frequency and pull-in voltage due to geometrical dimension changes and stress induced. The main purpose of this work is to understand the effect of bending on the device characteristics by means of finite element analysis. Another objective of the work is to understand the relationships between such an effect and the device geometries. It is learned that the bending-induced stress depends strongly on anchor width, membrane thickness, and substrate thickness. It is also learned that resonant frequency and pull-in voltage become lower in most cases because of using a flexible substrate in comparison to those of the device on a rigid substrate. Bending-induced stress increases the spring constant and hence increases resonant frequency and pull-in voltage, although this effect is relatively weaker. For most of the device geometries, pull-in voltage is too high for the polymer material to endure. This is the main drawback of the all-polymer CMUT. In order to meet the design goal of 20 MHz resonant frequency, the membrane radius has to be smaller than 7.7 mu m for a thickness of 3 mu m.Article Citation - WoS: 1Citation - Scopus: 5Understanding Intangible Aspects of Cultural Landscape; Living Cultures of Northeast Kayseri Valleys(Geleneksel Yayincilik Ltd Stl, 2021) Kevseroglu, Oztem; Ayatac, Hatice; Yoney, Nilufer Baturayoglu; Baturayoğlu Yöney, NilüferSustaining cultural landscapes requires the conservation of socio-cultural characteristics as well as their physical manifestations. It is essential to document and conserve tangible and intangible elements of heritage in an integrated manner as cultural heritage consists of "both tangible and intangible works through which the creativity of a people finds expressions". These include but may not be limited to social practices, daily lives, rituals, traditional craftsmanship, know-how, techniques and skills, historic places, buildings, public spaces and objects. Finding the means of understanding and safeguarding intangible cultural heritage and its transmission to next generations is vital for the preservation of tangible heritage and its characteristics. This paper reviews the development of the concepts of intangible cultural heritage and cultural landscapes, and the interrelationship between tangible and intangible cultural heritage. Their interaction opens up new approaches to cultural heritage and its conservation. The case study focuses on the cultural landscape features of Kayseri's Northeast Valleys, Koramaz, Gesi and Derevenk, in terms of their tangible and intangible heritage elements and values. The methodology, therefore, proposes the integrated documentation and analysis of these tangible and intangible cultural heritage characteristics. The area had a multi-cultural, ethnic and religious social structure, which shaped its elements through human-nature interaction. However, demographic changes within the last century transformed daily-life practices. The research is based on in-depth interviews with local residents, analysis of archival sources and documentation of the physical remains in the field. The results highlight the traditional crafts and production techniques as daily-life practices; some of these are still continued at the present while others are not practiced anymore. Those practiced in the recent past are carried to our day through the remembrances and accounts of the elders. The documentation of these practices forms the first step for their revival and sustainability for the future and provide valuable tools for the development of principles and strategies with this purpose. Understanding the physical, natural and socio+ layers of tangible and intangible cultural heritage is essential in this context. Their promotion and the inclusion of local stakeholders in the conservation process is the only solution for the integrated conservation of these cultural landscapes in terms of a living heritage approach.