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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14411/18
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Article Influence of Synthesis Parameters on the Structural Formation of Mayenite via the Citrate Sol-Gel Method(Tubitak Scientific & Technological Research Council Turkey, 2025) Eryildirim, Busra; Oktar, Nuray; Dogu, DorukMayenite (Ca12Al14O33) has remarkable properties such as high oxygen mobility, ionic conductivity, and catalytic activity. It has many different applications, including oxide-conducting electrolytes, fluorescent lamps, moisture sensors, hydrogen-permeable membranes, oxygen pumps, hydrogen storage, and catalysis. However, pure and homogeneous mayenite synthesis parameters have not yet been fully explored. This study examines the effect of synthesis parameters including metal salt (MS) to citric acid (CA) molar ratios (1:1 and 1:2), pH (0.4-2), and calcination temperature (900-1200 degrees C) in citrate sol-gel method on the crystal structure of mayenite. Synthesized materials were examined by thermogravimetric (TG), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, N2 adsorption-desorption, scanning electron microscopy (SEM), inductively coupled plasma-optical emission spectrometry (ICP-OES), Fourier-transform infrared spectroscopy (FTIR), and pyridine adsorbed diffuse reflectance Fourier-transformed infrared spectroscopy (DRIFTS) analyses. The results show that all 3 parameters contribute to the mayenite phase formation and different impurity phases can be observed depending on the synthesis parameters. With no pH adjustment and an MS to CA ratio of 1, other phases of calcium aluminate mostly form. Mayenite becomes the main phase by doubling the CA amount. Besides CA, pH is also an important factor in mayenite synthesis. When the pH was adjusted to 2 with the MS to CA ratio at 1:1, mayenite was formed as the main phase, but other phases of calcium aluminate were also observed in the structure. XRD results show that all parameters studied influence the crystal structure of the final material, including the calcination temperature. This study shows that pure mayenite can be synthesized with a calcination temperature of 1200 degrees C, at a pH of 2, and the MS to CA molar ratio of 1:2.Article W-Band RCS Prediction of Small Objects: Comparing Two Widely Used Methods with Experimental Validation(Gazi University, 2025) Kara, Ali; Aydın, Elif; Yardım, Funda Ergün; Sezgin, Deniz; Ergun Yardim, FundaThis paper compares the accuracy of Shooting and Bouncing Rays and Electric Field Integral Equation methods for Radar Cross Section prediction of small objects at 77-81 GHz band. Existing studies on RCS prediction methods often lack comprehensive comparisons between computational and experimental results, particularly for small objects measured with a 77 GHz radar. This study addresses this gap by presenting an in-depth analysis of both simulation and measurement data. In this work, three targets with varying geometries and materials were measured with a frequency modulated continuous wave radar and simulated using Ansys HFSS and CST Studio Suite. The measurements were performed with a commercial off-the-shelf (COTS) frequency modulated continuous wave radar operating at 77–81 GHz. This study aims to emphasize the importance of considering both efficiency and accuracy when opting for an RCS prediction method. Overall, the outcomes of both methods have largely demonstrated good alignment. It has been noted that, while Shooting and Bouncing Rays method offers promising time-saving advantages, Electric Field Integral Equation method remains a valuable tool for complex geometries where precise results are crucial.Article Citation - WoS: 1Citation - Scopus: 1On Some Permutation Trinomials in Characteristic Three(Hacettepe Univ, Fac Sci, 2025) Temür, Burcu Gülmez; Özkaya, Buket; Gülmez Temür, BurcuIn this paper, we determine the permutation properties of the polynomial x3 +xq+2 −x4q−1 over the finite field Fq2 in characteristic three. Moreover, we consider the trinomials of the form x4q−1 + x2q+1 ± x3. In particular, we first show that x3 + xq+2 − x4q−1 permutes Fq2 with q = 3m if and only if m is odd. This enables us to show that the sufficient condition in [34, Theorem 4] is also necessary. Next, we prove that x4q−1 + x2q+1 − x3 permutes Fq2 with q = 3m if and only if m ̸≡ 0 (mod 4). Consequently, we prove that the sufficient condition in [20, Theorem 3.2] is also necessary. Finally, we investigate the trinomial x4q−1 + x2q+1 + x3 and show that it is never a permutation polynomial of Fq2 in any characteristic. All the polynomials considered in this work are not quasi-multiplicative equivalent to any known class of permutation trinomials.Article Citation - WoS: 3Citation - Scopus: 1Caval Valve Implantation Procedure in 7 Cases of Torrential Tricuspid Regurgitation and Step-By Description of the Procedure(Kare Publ, 2025) Sarıçam, Ersin; Barcin, Cem; Çelebi, Aksüyek Savaş; Asfour, Mohamed; Bozbas, Huseyin; İlkay, Erdoğan; Cam, Ersin; Celebi, Savas A.Tricuspid regurgitation (TR) is an increasingly prevalent and clinically significant health problem.1 Due to the growing understanding of the importance of TR, the tricuspid valve has transitioned from being a forgotten valve to one of significant concern. Tricuspid regurgitation is often functional, and as it progresses to moderate or severe stages, hospital admissions increase and prognosis worsens.1,2 There are no effective pharmacological treatments for TR, and the 5-year survival rate with medical management is reported to be less than 50%.3 Therefore, early diagnosis and timely intervention for TR is crucial. Both surgical and percutaneous treatment options are available for severe TR. The mortality rate for isolated TR surgery is generally high.4 In recent years, transcatheter treatments have become feasible for this patient group, and accumulating evidence shows that transcatheter treatment is superior to medical management.5,6 Transcatheter interventions for TR can be performed in 4 ways, 2 involving repair and 2 involving valve We aimed to present our experience with transcatheter caval valve implantation (CAVI) in 7 patients with torrential TR who were not suitable for surgical intervention or transcatheter edge-to-edge repair (T-TEER) due to severe coaptation defects, review the current literature, and provide a step-by-step description of the procedure.Article Citation - WoS: 22Citation - Scopus: 23A COUPLED FIXED POINT RESULT IN PARTIALLY ORDERED PARTIAL METRIC SPACES THROUGH IMPLICIT FUNCTION(Hacettepe Univ, FAC Sci, 2013) Özyurt, Selma Gülyaz; Karapınar, Erdal; Gulyaz, SelmaIn this manuscript, we discuss the existence of coupled fixed points inthe context of partially ordered metric spaces through implicit relationsfor mappings F : X× X -> X such that F has the mixed monotoneproperty. Our main theorem improves and extends various results inthe literature. We also state an example to illustrate our workArticle On Pairs of $ell$-Köthe Spaces(Hacettepe Univ, FAC Sci, 2010) Karapınar, ErdalLet $ell$ be a Banach sequence space with a monotone norm $parallel centerdot parallel_{ell}$, in which the canonical system ($e_i$) is a normalized unconditional basis. Let $a = (a_i), a_i rightarrow infty, lambda=(lambda_i)$ be sequences of positive numbers. We study the problem on isomorphic classification of pairs $F = biggl(K^{ell} biggl( exp biggl(-frac{1}{p}a_i biggr)biggr),K^{ell}biggl(exp biggl(-frac{1}{p}a_i + lambda_i biggr)biggr)biggr)$. For this purpose, we consider the sequence of so-called m-rectangle characteristics $mu^F_m$. It is shown that the system of all these characteristics is a complete quasidiagonal invariant on the class of pairs of finite-type $ell$-power series spaces. By using analytic scale and a modification of some invariants (modified compound invariants) it is proven that m-rectangular characteristics are invariant on the class of such pairs. Deriving the characteristic $tilde{beta}$ from the characteristic $beta$, and using the interpolation method of analytic scale, we are able to generalize some results of Chalov, Dragilev, and Zahariuta (Pair of finite type power series spaces, Note di Mathematica 17, 121–142, 1997).Article Tests of Rationality in the Turkish Foreign Exchange Market(Central Bank Republic Turkey, 2014) Topbas, Neslihan; International Trade and LogisticsThe rationality of expectations has been tested in many foreign exchange markets using survey data. This study is aimed at gaining empirical insights about the expectations of market participants in the Turkish foreign exchange market. Using survey data provided by Central Bank of Turkey on the exchange rate of the Turkish lira against the US dollar, it is determined that the mean of expectations of market participants for one year and one month ahead were higher than the mean of actual depreciation. The analysis resulted in rejection of the popular test for forward exchange rate unbiasedness in predicting the future spot exchange rate. Another test of rationality has also been checked and the result has been rejection as well, which can be interpreted that the forward premium contains additional information for exchange rate forecasts.Article Citation - WoS: 2Citation - Scopus: 2Regional Variations in Psoriatic Arthritis: Insights From a Nationwide Multicenter Analysis in Türkiye(Turkish League Against Rheumatism, 2024) Kılıç, Erkan; Kılıç, Gamze; Tekeoğlu, İbrahim; Sargın, Betül; Kasman, Sevtap Acer; Alkan, Hakan; Nas, Kemal; Yurdakul, Ozan Volkan; Duruöz, Mehmet Tuncay; Ayhan, Fikriye Figen; Bodur, Hatice; Kandur, Yaşar; Sunar, İsmihanObjectives: The study aimed to investigate and compare clinical features, disease activity, and the overall disease burden among psoriatic arthritis (PsA) patients across seven distinct geographic regions in Türkiye. Patients and methods: A multicenter cross-sectional study involving 1,134 PsA patients from 25 referral centers across seven regions was conducted. Demographic and clinical characteristics, comorbidities, joint involvement, extra-articular manifestations, and disease activity measures were evaluated across regions. Results: A total of 1134 PsA patients from seven different geographic regions in Türkiye participated in this study. The highest number of participants was from the Marmara region (n=409), with subsequent representation from Central Anatolia (n=370), Aegean (n=139), Mediterranean (n=60), Black Sea (n=60), Eastern Anatolia (n=60), and Southeastern Anatolia (n=36) regions. There were significant variations in demographic profile, including age, body mass index, age of disease onset, educational status, comorbidities, and family history of both psoriasis and PsA. Clinical features, such as enthesitis, dactylitis, uveitis, and joint involvement, demonstrated significant variation across regions. Additionally, disease activity measures, including pain, patient and physician global assessments, acute phase reactants, disease activity indices, quality of life, and functional status, displayed considerable regional differences. Conclusion: This nationwide study revealed substantial regional diversity in demographic data, clinical characteristics, disease activity, and quality of life among PsA patients in Türkiye. These findings stress the need to customize treatment approaches to address regional needs and to conduct further research to uncover reasons for disparities. It is crucial to enhance region-specific approaches to improve patient care and outcomes for PsA.Article A Modeling Approach for Designing New Acoustic Materials(Gazi Univ, 2024) Koçyiğit, Filiz Bal; Köse, Ercan; Buluklu, Hatice Mehtap; Bal Kocyigit, FilizIn this study, mathematical modeling design based on Sound Transmission Loss measurement results of new acoustic material samples with natural content was carried out. Using the test samples in question, transfer function of acoustic materials based on electronic filter circuit design and a transition design method for the production of new acoustic materials by utilizing the transfer function is presented. Based on the experimental results of the test samples, it is the most suitable low-pass filter structure for the proposed design. In this study, active Sallen-Key low-pass filter structure is preferred and used. Sound Transmission Losses in dB (decibels) of acoustic samples were obtained experimentally for 500, 1000, 2000 and 4000 Hz. fundamental frequencies in the literature. Based on these data, transfer function simulation suppression gain results were obtained in TINA-TI program, active filter circuit designed, and MATLAB program. When the other results were compared in the experimental results, it was seen that very close values were obtained. It has been demonstrated that the proposed method can be used effectively in the design and examination of new acoustic materials.Article Citation - WoS: 2Measuring Dependence Between Electricity Consumption and Economic Indicators Via Copulas: Turkish Case(Gazi Univ, 2018) Evkaya, O. Ozan; Yozgatligil, Ceylan; Selcuk-Kestel, A. Sevtap; Kestel, A. Sevtap Selçuk; MathematicsThis paper implements copulas to identify the dependence structure between electricity consumption and its cofounding indicators. To achieve this, Turkish electricity demand, its economic and sectoral indicators are taken into account. As a first step, bivariate copulas are used to identify the best fitting copula and the degree of the dependence. Thereafter, multivariate model is established using vine copulas using highly correlated variables. The empirical results confirm the added value of the proposed approach in determining numerous tail properties. We indicate that the copulas are useful to underline, especially, the tail properties of indicators in the market for decision makers.