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Article Citation - WoS: 1Citation - Scopus: 1Mikro Frezeleme İşleminin Takım Eksen Sapması Göz Önüne Alınarak Mekanistik Modellemesi(Gazi Univ, Fac Engineering Architecture, 2018) Karpat, Yiğit; Kanlı, Muammer; Olıaeı, Samad Nadimi Bavilİşlenmesi zor malzemelerden yapılan mikro parçaların hassas üretiminde mikro frezeleme yaygın olarakkullanılan bir yöntemdir. Malzeme işleme hızının yüksek olması ve işleme sonunda iyi yüzey kalitesiüretilmesi bu yöntemin en belirgin avantajlarıdır. Mikro frezeleme işleminin sonuçlarının tahminedilebilmesi için ilk adım hassas bir mekanistik kuvvet modelinin geliştirilmesidir. Mikro frezelemedeoluşan ortalama kesme kuvvetlerinin ilerlemeye göre değişimi makro ölçek frezelemede olduğu gibidoğrusal bir karakteristik göstermez. Bu çalışmada, kübik polinom karakteristiğine sahip ortalama kuvvetmodeline dayalı bir mekanistik model geliştirilmiştir. Ek olarak mikro takımın eksenel sapması geliştirilenmekanistik modele dahil edilmiştir. Geliştirilen model ile titanyum Ti6Al4V alaşımının işlemesi sırasındatahmin edilen kuvvetlerin yapılan ölçümler ile uyumlu olduğu görülmüştür. Farklı işleme şartlarında takımeksenel sapmasının değeri geliştirilen model vasıtası ile araştırılmıştır.Review Boşluklu Perde Duvar Sistemlerin Serbest Titreşim Periyotlarının Farklı Yöntemlerle Hesaplanması(2003) Akış, Tolga; Coşkun, Safa BozkurtÇok katlı betonarme yapılarda kullanılan boşluklu perde duvarlar, özellikle deprem dayanımları açısından sıkça tercih edilen yapı sistemleridir. Dayanım ve rijitlik bakımından olumlu özelliklere sahip boşluklu perde duvarların, boşluksuz perde duvarlara göre daha sünek davrandığı bilinmektedir. Herhangi bir yapısal sistemin deprem davranışını belirleyen en önemli parametreler sistemin doğal modları ve bu modlara ait periyotlardır. Bu çalışmada, daha önce sınır eleman yöntemi kullanılarak modellenmiş ve serbest titreşim periyottan elde edilmiş bir boşluklu perde duvar sistemin, gerilme elemanlarının kullanıldığı sonlu elemanlar yöntemi ve çubuk elemanların kullanıldığı geniş kolon benzeşimi yöntemi kullanılarak serbest titreşim periyotları bulunmuştur. Analizlerden çıkan sonuçlar karşılaştırılmıştır.Article Electrochemical and Optical Properties of an Azo Dye Based Conducting Copolymer(2009) Cihaner, Atilla; Algı, FatihThe electrochemical and optical properties of a novel conducting copolymer called poly(2,5' -dimethyl-[4- (2,5-di-thiophen-2-yl-pyrrol-1-yl)-phenyl]azobenzene-co-(3,4-ethylenedioxythiophene)) (poly(1-co-EDOT)) are reported. Electrochemically synthesized poly(1-co-EDOT) based on the azo dye has a well-defined and reversible redox couple (0.37 V vs. Ag/AgCl) with good cycle stability. The copolymer film exhibits high conductivity (13 S/cm) as well as electrochromic behavior (magenta when neutralized and transmissive sky blue when oxidized). Furthermore, electro-optically active copolymer film has a low band gap of 1.79 eV with a π − π* transition at 555 nm.Article Isı Etkisi Altındaki Fonksiyonel Derecelendirilmiş Malzemeden Yapılmış Uzun Tüplerde Plastik Akmanın Başlaması(2006) Akış, Tolgaİçerisinde düzgün olmayan ısı üreten, fonksiyonel derecelendirilmiş malzemeden yapılmış uzun bir tüpün elastik davranışı analitik olarak incelenmiştir. Tüpün ısı iletim katsayısının ve elastisite modülünün radyal koordinat boyunca lineer olmayan formda değiştikleri varsayılmıştır. Tresca akma kriteri kullanılarak, fonksiyonel derecelendirme parametrelerinin tüpteki plastik akmanın başlangıcına etkileri incelenmiş, akmanın bu parametrelere bağlı olarak önce iç yüzeyden, önce dış yüzeyden, ya da tüpün iç bölgesinden başlayabileceği gözlenmiştir.Article Citation - WoS: 7Citation - Scopus: 10Ann-Assisted Forecasting of Adsorption Efficiency To Remove Heavy Metals(Tubitak Scientific & Technological Research Council Turkey, 2019) Buaısha, Magdi; Balku, Şaziye; Yaman, Şeniz ÖzalpIn wastewater treatment, scientific and practical models utilizing numerical computational techniques suchas artificial neural networks (ANNs) can significantly help to improve the process as a whole through adsorption systems.In the modeling of the adsorption efficiency for heavy metals from wastewater, some kinetic models have been used such as pseudo first-order and second-order. The present work develops an ANN model to forecast the adsorption efficiency of heavy metals such as zinc, nickel, and copper by extracting experimental data from three case studies. To do this, we apply trial-and-error to find the most ideal ANN settings, the efficiency of which is determined by mean square error (MSE) and coefficient of determination (R2). According to the results, the model can forecast adsorption efficiency percent (AE%) with a tangent sigmoid transfer function (tansig) in the hidden layer with 10 neurons and a linear transferfunction (purelin) in the output layer. Furthermore, the Levenberg–Marquardt algorithm is seen to be most ideal for training the algorithm for the case studies, with the lowest MSE and high R2 . In addition, the experimental results and the results predicted by the model with the ANN were found to be highly compatible with each other.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, DenizThis 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: 7Citation - Scopus: 10Comparison of Three Different Learning Methods of Multilayer Perceptron Neural Network for Wind Speed Forecasting(Gazi Univ, 2021) Bulut, Mehmet; Tora, Hakan; Buaisha, Dr.magdiIn the world, electric power is the highest need for high prosperity and comfortable living standards. The security of energy supply is an essential concept in national energy management. Therefore, ensuring the security of electricity supply requires accurate estimates of electricity demand. The share of electricity generation from renewables is significantly growing in the world. This kind of energy types are dependent on weather conditions as the wind and solar energies. There are two vital requirements to locate and measure specific systems to utilize wind power: modelling and forecasting of the wind velocity. To this end, using only 4 years of measured meteorological data, the present research attempts to estimate the related speed of wind within the Libyan Mediterranean coast with the help of ANN (artificial neural networking) with three different learning algorithms, which are Levenberg-Marquardt, Bayesian Regularization and Scaled Conjugate Gradient. Conclusions reached in this study show that wind speed can be estimated within acceptable limits using a limited set of meteorological data. In the results obtained, it was seen that the SCG algorithm gave better results in tests in this study with less data.Article Correlation of Clinical Signs and Magnetic Resonance Imaging Findings in Patients With Lumbar Spondylosis(Turkish League Against Rheumatism, 2023) Altan, Lale; Ökmen, Burcu Metin; Tuncer, Tiraje; Sindel, Dilşad; Çay, Hasan Fatih; Hepgüler, Simin; Uğurlu, HaticeObjectives: The purpose of the study was to contribute further to this debated topic by investigating the correlation of magnetic resonance imaging (MRI) findings with the clinical picture in lumbar spondylosis patients. Patients and methods: This multicenter retrospective study (as part of the epidemiological project of the TLAR-OASG [Turkish League Against Rheumatism-Osteoarthritis Study Group]) included 514 patients (101 males, 413 females; mean age: 63.6±10.8 years; range, 40 to 85 years) who were diagnosed as lumbar spondylosis by clinical examination and direct X-ray between December 2016 and June 2018. Demographic characteristics of patients, Visual Analog Scale for pain, presence of radiating pain, Roland-Morris disability questionnaire, straight leg raise test, deep tendon reflexes, neurogenic intermittent claudication symptoms, any decrease of muscle strength, and abnormality of sensation were recorded. Lumbar MRI findings of the patients were recorded as positive or negative in terms of disc herniation, intervertebral disc degeneration, root compression, osteophytes, spinal stenosis. Statistical analysis was done to assess the correlation between the clinical symptoms, physical examination, and MRI findings. Results: Correlation analysis of the MRI results and the clinical findings showed a significant correlation between straight leg raise test and root compression (p<0.001, r=0.328) and a significant correlation between neurogenic intermittent claudication and spinal stenosis (p<0.001, r=0.376). Roland-Morris disability questionnaire had a significant correlation with all MRI findings (p<0.05, r<0.200). Conclusion: The results of this study corroborate the notion that diligent patient history and physical examination are more valuable than MRI findings, even though a higher incidence of abnormal MRI findings have been obtained in patients with disability and dermatomal radiating pain.Article A Modeling Approach for Designing New Acoustic Materials(Gazi Univ, 2024) Koçyiğit, Filiz Bal; Köse, Ercan; Buluklu, Hatice MehtapIn 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: 4Citation - Scopus: 5Construction of a Complex Jacobi Matrix From Two-Spectra(Hacettepe Univ, Fac Sci, 2011) Guseinov, Gusein Sh; MathematicsIn this paper we study the inverse spectral problem for two-spectra of finite order complex Jacobi matrices (tri-diagonal matrices). The problem is to reconstruct the matrix using two sets of eigenvalues, one for the original Jacobi matrix and one for the matrix obtained by deleting the first column and the first row of the Jacobi matrix. An explicit procedure of reconstruction of the matrix from the two-spectra is given.
