26509 research outputs found
Sort by
The Relationship between Public Expenditures and Economic Growth in the Scope of Economic Classification: The Case of Turkiye
Full text linkThe relationship between public expenditures and economic growth is a constantly debated topic among researchers. There are five main models used to test Wagner's Law. This study aims to test Wagner's Law for Turkiye's public expenditure and expenditure types within the scope of economic classification by using all models in the literature. We tested the validity of Wagner's Law in the Turkiye case using the ARDL method applied for the years 1950-2020. Study findings prove that Wagner's Law is valid in Turkiye using the Mann and Peacock models for public expenditure. In addition, the findings support Wagner's Law only in transfer expenditures among sub-components. These findings point out that public expenditure, which increases more than gross domestic product, is dominated by transfer expenditures. The fact that social transfers account for approximately 75% of transfer expenditures in the last decade demonstrates that Turkiye prioritizes the social state function
Extensions of Simpson's Inequality via Nonnegative Weight Functions and Fractional Operators
No full textIn this paper, we present a new version of Simpson-type inequalities for differentiable functions defined on a subinterval of the positive real axis. The approach involves a nonnegative integrable weight function and provides an identity that refines the classical Simpson inequality by incorporating the first derivative of the function. A key aspect of this work is the inclusion of the Riemann-Liouville fractional integral, through which we derive specific inequalities that extend the classical framework. In certain cases, our results reduce to the well-known Simpson inequality, demonstrating the generality and flexibility of the method.MSC2020 Classification: 26A09, 26D10, 26D15, 33E2
The Effect of Self-Service Technology Quality on Novelty-Seeking and Revisit Intention in Restaurant Settings
No full textThis study explores how self-service technologies (SSTs) quality in restaurants influences customers' novelty-seeking behavior and their intention to revisit. Data were collected through surveys distributed via Amazon Mechanical Turk, comprising responses from 498 participants. Structural Equation Modeling (SEM) was used for data analysis to assess the relationships between perceived SST quality, novelty-seeking, and revisit intentions. The study identifies significant positive effects of SST quality dimensions such as enjoyment, security, and assurance on novelty-seeking. However, functionality, convenience, and customization were not significantly linked to novelty-seeking. Furthermore, novelty-seeking significantly impacted both affective and cognitive attitudes, which in turn influenced revisit intentions. Venturesomeness was examined as a moderating factor but only significantly moderated the relationship between cognitive attitudes and revisit intentions. Self-service technology quality directly influences customer engagement and satisfaction, leading to increased revisit intentions through the mediating role of novelty-seeking.USF M3 Center for Hospitality Technology InnovationThis work was supported by USF M3 Center for Hospitality Technology & Innovation
Delamination and thrust force analysis in GLARE: Influence of tool geometry and prediction with machine learning models
No full textThe multi-layered (fiber/metal) structure of glass fibre aluminium reinforced epoxy (GLARE) makes it difficult to obtain acceptable damage-free holes that meet aerospace standards. This paper investigated the effects of tool geometry and drilling parameters on reducing delamination damage and uncut fibers at the hole exit surface in drilling GLARE. The hole surfaces were examined by scanning electron microscope (SEM) at various magnifications. In addition, deep neural network (DNN) and long-short-term memory (LSTM) machine learning models were used to predict delamination (Fda), uncut fiber (UCF), and thrust forces using experimental data. No positive contribution of the special geometry tool was observed, while the standard geometry tool was found to be ideal for drilling conditions. Analysis of variance (ANOVA) revealed that feed rate contributed 57.83% to delamination damage, while tool geometry contributed 74.31% and 92.33% for uncut fiber and thrust force, respectively. SEM analysis revealed high deformation zones in the aluminum layers and fiber fracture and separation in the glass fibre reinforced polymer (GFRP) layers. DNN and LSTM models were found to provide accurate predictions with R2 values greater than 95% and 98%, respectively
Development of thermophysical properties of Gd2Zr2O7 ceramics for thermal barrier coating applications
No full textTermal Bariyer Kaplamalar (TBK), gaz türbinlerinde yüksek sıcaklığa sahip gaz akımlarına maruz kalan bileşenleri korumak, sistemin dayanıklılığını artırmak ve yakıt verimliliğini iyileştirmek amacıyla yaygın olarak tercih edilmektedir. Bu kaplama sistemleri, genellikle süper alaşım bir altlık üzerine uygulanan metalik bir bağ katmanı ve onun üzerinde yer alan seramik bir üst katmandan meydana gelir. Günümüzde en yaygın ve etkili Termal Bariyer Kaplama (TBK) malzemesi, %8 oranında itriyum oksit ile stabilize edilmiş zirkonya (YSZ) olarak öne çıkmaktadır. Yüksek sıcaklıklara karşı dayanıklı olan bu seramik kaplamalar, yaklaşık 1200?°C'ye kadar etkin bir şekilde kullanılabilmekte, düşük termal iletkenlikleri ve yüksek termal şok dayanımları sayesinde motor ve türbin sistemlerinde kritik bir koruma sağlamaktadır. Zirkonya, oda sıcaklığında monoklinik kristal yapıda bulunmakta; sıcaklığın artmasıyla 1170?°C'de tetragonal faza, 2370?°C'nin üzerinde ise kübik kristal yapıya dönüşmektedir. Bu faz geçişleri sırasında yaşanan %3-5 oranındaki hacim değişimi, kaplama bütünlüğünü bozarak servis ömrünü ciddi şekilde kısaltmaktadır. Bu nedenle, mevcut kaplama sistemlerinin yerine daha üstün termal, mekanik ve kimyasal özelliklere sahip yeni nesil malzemelerin geliştirilmesi, türbin bileşenlerinin ömrünü uzatmakta, bakım periyotlarını azaltmakta ve sistemin genel verimliliğini artırarak yüksek sıcaklık koşullarında daha güvenli çalışma koşulları sunmaktadır. Bu amaç doğrultusunda daha yüksek termal kararlılık, düşük termal iletkenlik ve yüksek termal genleşme gibi özellikleriyle Gd?Zr?O? (GZO) seramikleri öne çıkmaktadır. Bu seramikler termal bariyer kaplama sistemlerinde YSZ'ye alternatif bir malzeme olarak düşünülmektedir. Gd?Zr?O? (GZO) esaslı seramiklerin termal bariyer kaplamalarda (TBK) kullanımı, sahip oldukları avantajlı özellikler nedeniyle giderek yaygınlaşmaktadır. Ancak sınırlı kırılma tokluğu, nadir toprak elementlerine olan bağımlılık ve yüksek üretim maliyetleri gibi etkenler, bu malzemelerin sürdürülebilirliği açısından bazı zorluklar doğurmaktadır. Bu çalışmada, GZO seramikleri Fe, Mo ve Ti gibi nadir toprak elementi olmayan elementlerle ve Yb ile farklı oranlarda katkılanarak 8 adet numune üretilmiş ve bu katkılamanın mekanik ve termo-fiziksel özellikler üzerindeki etkisi araştırılmıştır. Katkısız GZO seramiği kusurlu florit (F) fazında, katkılı GZO seramikleri ise piroklor (P) fazında oluşmuştur. 900?°C'de katkısız GZO'nun termal iletkenliği 2,21?W.m-1.K-1 olarak ölçülmüşken, katkılı seramiklerde bu değer en düşük 0,89?W.m-1.K-1 seviyesine kadar düşmüştür. 1150?oC sıcaklıkta katkısız GZO'nun termal genleşme katsayısı 11,48?×?10-6.K-1 olarak belirlenmiş, katkılı GZO seramiklerinde ise bu değerler 10,39 ×?10-6.K-6 ile 11,88?×?10-6.K-6 arasında değişmiştir. Mekanik özellikler açısından, katkısız GZO'nun sertliği 10,88?GPa olarak ölçülmüş, katkılı seramiklerde bu değer 8,64?GPa ile 10,99?GPa arasında değişmiştir. Elastik modül katkısız GZO için 307?GPa iken, katkılı numunelerde 302 GPa ile 343?GPa arasında ölçülmüştür. Kırılma tokluğu katkısız GZO için 1,36?MPa.m1/2 olarak hesaplanmış, katkılı seramiklerde ise bu değer 0,92 MPa.m1/2 ile 1,64 MPa.m1/2 aralığında bulunmuştur. Bu bulgulara dayanarak, katkılı GZO seramiklerinin TBK uygulamaları için potansiyel taşıdığı sonucuna varılabilir. Ayrıca, bu seramiklerde nadir toprak elementlerine olan bağımlılığın azaltılması, daha sürdürülebilir ve çevre dostu kaplama malzemelerinin geliştirilmesine katkı sağlayabilir.Thermal Barrier Coatings (TBCs) are widely utilized in gas turbines to protect components exposed to high-temperature gas flows, enhance system durability, and improve fuel efficiency. These coating systems typically consist of a metallic bond coat applied onto a superalloy substrate, topped with a ceramic top coat. Today, the most common and effective TBC material is zirconia (ZrO2) stabilized with 8?wt.% yttria (Y2O3), known as 8YSZ. These ceramic coatings, which are highly resistant to elevated temperatures, can function effectively up to approximately 1200?°C and provide critical protection in engine and turbine systems thanks to their low thermal conductivity and high thermal shock resistance. Zirconia exists in a monoclinic crystal structure at room temperature; as the temperature rises, it transforms to a tetragonal phase at 1170?oC and to a cubic phase above 2370?oC. These phase transitions involve a volumetric change of about 3–5%, which compromises the integrity of the coating and significantly reduces its service life. Therefore, the development of next-generation materials with superior thermal, mechanical, and chemical properties is essential to replace current coatings. Such materials can extend the lifespan of turbine components, reduce maintenance intervals, and improve overall system efficiency while ensuring safer operation under extreme thermal conditions. In line with this goal, Gd2Zr2O7 (GZO) ceramics have emerged as promising candidates due to their higher thermal stability, lower thermal conductivity, and desirable thermal expansion properties. These ceramics are considered a potential alternative to YSZ in thermal barrier coating systems The use of Gd2Zr2O7 (GZO)-based ceramics in thermal barrier coatings (TBCs) has been increasingly widespread due to their advantageous properties. However, limited fracture toughness, dependence on rare-earth elements, and high production costs pose certain challenges to the sustainability of these materials. In this research, eight samples of GZO ceramics were produced by doping with various ratios of non-rare-earth elements such as Fe, Mo, and Ti, along with Yb, and the effects of these dopants on the mechanical and thermophysical properties were investigated. The undoped GZO ceramic exhibited a defective fluorite (F) phase, while the doped GZO ceramics formed in the pyrochlore (P) phase. At 900?oC, the thermal conductivity of undoped GZO was measured as 2,21?W.m-1.K-1, whereas in the doped ceramics, it decreased to as low as 0,89?W.m-1.K-1. At 1150?oC, the thermal expansion coefficient of undoped GZO was determined to be 11,48?×?10-6.K-1, while in the doped GZO ceramics, these values ranged from 10,39 ×?10-6.K-1 to 11,88?×?10-6.K-1. In terms of mechanical properties, the hardness of undoped GZO was measured as 10,88?GPa, while the doped ceramics exhibited hardness values ranging from 8,64 GPa to 10,99?GPa. The elastic modulus of the undoped GZO was 307?GPa, whereas the doped samples showed values between 302 GPa and 343?GPa. The fracture toughness of the undoped GZO was calculated as 1,36?MPa.m1/2, while for the doped ceramics, it ranged from 0,92 MPa.m1/2 to 1,64?MPa.m1/2. Based on these findings, it can be concluded that the doped GZO ceramics possess potential for TBC applications. Furthermore, reducing the reliance on rare-earth elements in these ceramics may contribute to the development of more sustainable and environmentally friendly coating materials
Statistical Convergence for Grünwald-Letnikov Fractional Differences: Stability, Approximation, and Diagnostics in Fuzzy Normed Spaces
Full text linkWe present a unified framework for fuzzy statistical convergence of Gr & uuml;nwald-Letnikov (GL) fractional differences in Bag-Samanta fuzzy normed linear spaces, addressing memory effects and nonlocality inherent to fractional-order models. Theoretically, we establish the uniqueness, linearity, and invariance of fuzzy statistical limits and prove a Cauchy characterization: fuzzy statistical convergence implies fuzzy statistical Cauchyness, while the converse holds in fuzzy-complete spaces (and in the completion, otherwise). We further develop an inclusion theory linking fuzzy strong Ces & agrave;ro summability-including weighted means-to fuzzy statistical convergence. Via the discrete Q-operator, all statements transfer verbatim between nabla-left and delta-right GL forms, clarifying the binomial GL discrete Riemann-Liouville correspondence. Beyond structure, we propose density-based residual diagnostics for GL discretizations of fractional initial-value problems: when GL residuals are fuzzy statistically negligible, trajectories exhibit Ulam-Hyers-type robustness in the fuzzy topology. We also formulate a fuzzy Korovkin-type approximation principle under GL smoothing: Ces & agrave;ro control on the test set {1,x,x2} propagates to arbitrary targets, yielding fuzzy statistical convergence for positive-operator sequences. Worked examples and an engineering-style case study (thermal balance with memory and bursty disturbances) illustrate how the diagnostics certify robustness of GL numerical schemes under sparse spikes and imprecise data
Canonical correlation analysis of the relationship between human development and environmental pressures in Türkiye: An analysis of socioeconomic and ecological indicators
No full textBu çalışma, Türkiye'nin insani gelişmişlik endeksi (İGE) ile çevresel baskılar (karbondioksit emisyonları ve malzeme ayak izi) arasındaki ilişkileri kanonik korelasyon analizi yöntemi ile incelemektedir. Sürdürülebilir kalkınma, ekonomik büyüme ve sosyal gelişim ile çevresel bozulmanın dengelenmesini hedeflemektedir. Ancak, bu iki alan arasındaki ilişkilerin karmaşıklığı, özellikle gelişmekte olan ülkelerde sürdürülebilir kalkınma politikalarının başarısı için kritik bir öneme sahiptir. Bu çalışmada, 1990-2022 yılları arasında Türkiye'nin İGE verileri ile çevresel göstergeler arasındaki ilişkiler değerlendirilmiştir. Analiz sonuçlarına göre, Türkiye'de ekonomik büyüme ile çevresel baskılar arasında güçlü bir ilişki tespit edilmiştir. Özellikle karbondioksit emisyonları ve malzeme ayak izi, ekonomik büyüme ile artış eğilimindedir. Çalışma, ekonomik büyümenin çevresel sürdürülebilirliği tehdit edebileceğini ortaya koymakta ve Türkiye'nin sürdürülebilir kalkınma hedeflerine ulaşabilmesi için çevre dostu politikaların hayata geçirilmesi gerektiğini vurgulamaktadır. Enerji verimliliği, çevre dostu teknolojilerin kullanımı ve çevresel farkındalık artırıcı stratejilerin geliştirilmesi, sürdürülebilir kalkınmanın sağlanması açısından önemli öneriler arasında yer almaktadır.This study examines the relationship between Türkiye’s human development index (HDI) and environmental pressures (carbon dioxide emissions and material footprint) using canonical correlation analysis. Sustainable development aims to balance economic growth and social development with environmental degradation. However, the complexity of the relationships between these two areas is critical for the success of sustainable development policies, especially in developing countries. In this study, the relationship between Türkiye’s HDI data and environmental indicators between 1990 and 2022 is analyzed. According to the results of the analysis, there is a strong relationship between economic growth and environmental pressures in Türkiye. In particular, carbon dioxide emissions and material footprints tend to increase with economic growth. The study reveals that economic growth may threaten environmental sustainability and emphasizes that environmentally friendly policies should be implemented for Türkiye to achieve its sustainable development goals. Energy efficiency, the use of environmentally friendly technologies and the development of strategies to raise environmental awareness are among the important recommendations in terms of ensuring sustainable development
WO3-decorated TiO2 photocatalysts for enhanced selectivity and activity under UVA irradiation in aqueous oxidation of 3-methylpyridine and 3-pyridinemethanol
Full text linkTiO2/WO3 nanocomposites with varying WO3 loadings were synthesized via a sol-gel method under acidic conditions (pH 1) and comprehensively evaluated for the selective photocatalytic oxidation of 3-methylpyridine and 3-pyridinemethanol in aqueous solution. Structural and surface analyses (XRD, BET, SEM-EDX, XPS, DRS, PL, and photocurrent measurements) confirmed the successful formation of TiO2/WO3 heterojunctions, which facilitated efficient charge separation and suppressed recombination. Compared with pristine TiO2 and WO3, the composites exhibited superior photocatalytic activity and selectivity toward valuable carbonyl compounds, namely 3-pyridinemethanal and vitamin B3. While pristine WO3 displayed negligible photocatalytic activity and poor selectivity, commercial anatase TiO2 showed low activity and selectivity for 3-methylpyridine oxidation, but moderate performance for 3-pyridinemethanol oxidation. Among the series, TiO2-0.7WO3-300 showed the highest performance, affording a total 3-pyridinemethanal and vitamin B3 yield of 40.2 % under UVA irradiation at neutral pH and up to 50 % vitamin B3 yield under acidic conditions (pH 3). Radical scavenging experiments demonstrated that superoxide radicals were the dominant species for selective oxidation. Additional adsorption studies revealed that substrate-catalyst interactions play a critical role in influencing activity, while pHdependent experiments indicated that the reaction medium strongly affects both the oxidation pathway and product distribution. Reusability and stability tests confirmed that the photocatalysts retained their efficiency over multiple cycles. Despite enhanced activity under UVA and UV-Vis light, the composites were inactive under visible light alone for 3-pyridinemethanol oxidation. These findings highlight TiO2/WO3 nanocomposites as robust and environmentally friendly photocatalysts for the selective synthesis of industrially relevant chemicals.Scientific Research Projects Coordination Unit (University of Afyon Kocatepe) [23.FENBIL.03]Authors would like to thank Scientific Research Projects Coordination Unit (University of Afyon Kocatepe (Project no.: 23.FENBIL.03), Eng. Mehmet Akkas (Iltem, Dumlup & imath;nar University, Turkiye) and Dr. Beyza Y & imath;ld & imath;r & imath;m Tuerkmen (TEAM, Dokuz Eyluel University) for SEM-EDX analyses, Dr. S. Alper Akal & imath;n (EMUM, Dokuz Eyluel University) for DRS analyses, Dr. Hakan S , ahin and Serhat T & imath;k & imath;z (TUAM, University of Afyon Kocatepe, Tuerkiye) for XRD and BET analyses, respectively
Türkiye’de Geometrik Düşünme Üzerine Yazılmış Tez Çalışmalarının İncelenmesi
No full textBu çalışmanın amacı Türkiye’de geometrik düşünmeyi konu alan yüksek lisans ve doktora tez çalışmalarının eğilimleri hakkında genel bir bilgi edinmektir. Çalışmada nitel araştırma kapsamında doküman incelemesi kullanılmıştır. Çalışmanın veri kaynaklarını 2000-2023 yılları arasında Türkiye’de geometrik düşünme üzerine hazırlanan 126 tez çalışması oluşturmaktadır. Tezler hazırlanan Tez İnceleme Formuna göre incelenmiştir. Çalışma sonucunda geometrik düşünme üzerine hazırlanan tezlerin büyük çoğunluğunda van Hiele Geometrik Düşünme Teorisinin kullanıldığı görülmüştür. En çok araştırılan konu alanının başarı olduğu ortaya çıkmıştır. Tezlerin yıllara göre dağılımının düzenli bir şekilde olmasa da son yıllarda genel olarak artış gösterdiği belirlenmiştir. Yüksek lisans düzeyinde tez çalışmalarında nicel, doktora düzeyinde tez çalışmalarında ise karma araştırma yönteminin daha fazla kullanıldığı görülmüştür. Ortaokul öğrencileri ile daha fazla sayıda çalışma yürütülmüştür. Veri toplama aracı olarak sıklıkla testlerin kullanıldığı görülmüştür. Tezlerin sonuçlarına göre farklı öğrenme ortamlarının öğrencilerin geometrik düşünme düzeylerini ve zihnin geometrik alışkanlıklarını artırmada etkili olduğu görülmüştür. Araştırma sonucunda ortaya konulan sonuçların geometrik düşünme ile ilgili çalışma yapacak olan araştırmacılara yol göstereceği düşünülmektedir
Safety assessment for different crest raising scenarios of earth dams
No full textThis study evaluates the effect of raising earth dams on their safety against seepage and slope stability. A zoned earth dam is considered without a drain, then with a horizontal drain. The effect of the dam raising method is evaluated through two scenarios. Scenario 1 proposes raising the dam's whole body, while scenario 2 suggests raising the downstream part only, using a retaining wall and downstream backfill. The two scenarios are assessed by raising 10%, 20%, and 30% of the original dam's height. For scenario 1, different hydraulic conductivities for the raised core were evaluated. For scenario 2, different downstream backfilling materials and slopes were investigated. The results show that dam raising increases the seepage discharge and reduces the downstream slope stability, especially if a high-permeability material is used to raise the core or a low-permeability material is used for the downstream backfill. The importance of the downstream drain is also highlighted