Yazar "Kurt, Mustafa" seçeneğine göre listele

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    Analysis of Acoustic Signals of Footsteps from the Piezoelectric Sensor
    (2023) Çiftçi, Bilge Çiğdem; Kaya, Gamze; Kurt, Mustafa
    Some materials can change their electrical polarization under the influence of a mechanical stress due to the piezoelectric effect. This stress-induced change in polarization produces a potential difference across the material. For this reason, the piezoelectric material generates an electrical signal when it is subjected to a pressure from acoustic energy. In this study, analysis of acoustic signals of footsteps from the piezoe-lectric sensor, especially for human footsteps, have been studied by considering the analytical relationship between the electrical signal generated from the sensor and the acoustic signal that provides the effect. We analyzed the acoustic signal data by assuming that the electrical output voltage of the piezoelectric sensor completely coincides with the frequency of the acoustic signals. The original signal was pre-processed using filtering systems and analyzed by the fast Fourier transform and power spectral density methods to extract descriptive spectral features of the signal. This preliminary study proposed a method as a sensor based piezoelectric security system to detect the acoustic signals that can indicate possible dangers to the safety of people or property. The source of the acoustic signal can be determined by matching it with the existing database using machine learning algorithms like face recognition systems for future goals.
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    Cutting Rate and Surface Characteristic Analysis in CNC Wire Electrical Discharge Machining of Aluminium Bronze
    (Univ Osijek, Tech Fac, 2019) Evran, Savas; Mutlu, Bilcen; Kurt, Mustafa
    In this study, cutting rate and surface characteristic analysis in wire electrical discharge machining of aluminium bronze were investigated. Cutting rate analyses were performed according to Taguchi L18 (2(1)x3(2)) orthogonal array. Machining parameters such as wire type, duration between two pulses (Br) and pulse time (AT) were used as control factors. Raw data obtained for cutting rate were converted to S/N ratio values. Optimum levels of the machining parameters for cutting rate were determined using analysis of signal-to-noise (S/N) ratio. Significant machining parameters and their percentage contributions on results were obtained using Analysis of Variance (ANOVA). Regression analysis was performed to model the relationship between cutting rate and machining parameters. Analyses of surfaces machined of workpiece using both two wires for minimum and maximum cutting rate were observed using scanning electron microscope (SEM) and surface roughness device.
  • Küçük Resim
    Öğe
    Design of EM-artifact-free earphone based on the photoacoustic effect
    (Elsevier GmbH, 2021) Muşdal, Bengi Derya; Kurt, Mustafa
    Electromagnetic interactions between conventional earphones and the electroencephalography (EEG) electrodes used for analyzing brain waves give rise to efficiency problems in neurophysiological studies of auditory perception. Currently used speakers and headphones are electromagnetic devices based on strong magnets. In spite of intensive use of such systems, there has been no effective way to eliminate the electromagnetic artifacts produced by such audio transmitting devices to date. The ability for transferring audible sounds without the use of electromagnetic devices that can affect the EEG signal would open up many innovative possibilities in Audio Technologies. Audible sound transfer over long distances is possible by the photoacoustic effect. In such studies, the modulated optical signal can be converted into an audible signal arising from the absorption of the light energy of relevant molecules. In this study, we propose an earphone based on the photoacoustic effect, and calculated the dB SPL (Sound Pressure Level) values for a spherical cell filled with olive pomace. By the use of the method of Diebold and Westervelt, we theoretically calculated the sound pressure levels for our cell and determined a 60 dB SPL at a sound frequency of 1000 Hz for our preliminary earphone design.
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    Determination of Absorption Coefficient of Chlorella Vulgaris and Arthrospira Maxima in Water
    (Amer Inst Physics, 2018) Tekiner, Murat; Kurt, Mustafa; Ak, Ilknur; Kurt, Arzu
    Safe drinking water is crucial for human healthy, nowadays all drinking and irrigation water in developed country commonly come from dams. The water is transported to our usage area by several type of pipe or water-trench. The water can be infected some bacteria such as Chlorella vulgaris, Arthrospira maxima, during this transportation. In this study, we determine which wavelength effect to these green algae and cyanobacteria. For different concentration of these microorganisms in water, we determined uv-vis spectrum. By analyzing these spectrums, we determined absorption coefficient of these microorganisms for selected wavelength. The results show which wavelength can be used for destroy these microorganisms in affected water.
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    Evaluation of Cross-Section and Wing Length in Free Vibration Analysis ofAircraft Wings
    (2020) Evran, Savas; Kurt, Mustafa; Kurt, Arzu
    This study presents the numerical free vibration analysis of aircraft wings created using different airfoil cross sections such as NACA 0009, NACA 2424, and NACA 4415. Aircraft wings were made of different lengths. Numerical frequency analyses were conducted Taguchi L9 orthogonal array with two control factors including three levels and so nine numerical modal analyses were performed. Airfoil cross sections and lengths of aircraft wings were used as the first and the second control factors. To detect the control factors with optimal levels, analysis of signal-to-noise (S/N) ratio was employed. In addition, analysis of variance (ANOVA) at the 95 % confidence level was implemented to carry out percent contributions of airfoil cross sections and lengths of aircraft wings on free vibration. As can be summarized from this study, the maximum free vibration behavior was obtained by using NACA 2424 wing profiles with a length of 5 meters. Also, the most dominant control factors were found to be airfoil type with 85.21 % effect and wing length with 12.87 % effect, according to ANOVA.
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    Fiber bragg grating yapımı ve uygulamaları
    (2006) Aydın, Ramazan; Esendemir, Akif; Kurt, Mustafa; Yılmaz, Özlem Kocahan; Atalay, Betül
    [Abstract Not Available]
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    Fiber optik jiroskobun teorisi ve bir uygulama olarak pasif yer tayini sisteminde kullanımı
    (Çanakkale Onsekiz Mart Üniversitesi, 2001) Kurt, Mustafa; Aydın, Ramazan
    oz Bu tezde, İnterferometrik Fiber Optik Jiroskobun (IFOG), temelleri incelenmiştir ; Sagnac Etkisinin temel prensipleri, karşılıklılık (reciprocity) ve mod türünün önemi, IFOG' daki hata kaynakları ve IFOG' un uygulama alanlarını tartışılmıştır. Buna ek olarak GPS' in (Küresel Konumlama Sistemi) temelleri, kullanımı ve hataları tartışılmıştır. IFOG, araç seyrüsefer sistemleri gibi endüstriyel ve kişisel uygulamaların çoğuna uygulanabilir. Yerleşim bölgelerinde, yalnızca GPS tabanlı pozisyon belirleme sistemleri, binalar tarafından bloklanma ve geriyansımalardan (multipath) oluşur. Bir IFOG tabanlı INS (İnertial Navigation System-Ataletsel Seyrüsefer Sistemi) sürekli bir pozisyon bilgisi sağlar. Fakat, bu sensörler kalibre edilebilir belirsizliklere sahiptir. Kararlılık, doğruluk ve sürekli çözümler veren iki navigasyon tekniğinin birleşimi olan bir sistem geliştirilir. Bu sistem bir GPS algılayıcısı, IFOG ve bir bilgisayardan oluşur. ODTÜ' de alan çalışmalarında sistemin deneme dataları alınmıştır. Anahtar Kelimeler : İnterferometrik Fiber Optik Jiroskop, GPS (Küresel Konumlama Sistemi), Sagnac Etkisi, karşılıklılık (reciprocity), INS (İnertial Navigation System-Ataletsel Seyrüsefer Sistemi), geriyansımalar (multipath)
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    Impact of UV-C radiation on growth of micro and macro algae in irrigation systems
    (Elsevier Science Bv, 2019) Tekiner, Murat; Ak, Ilknur; Kurt, Mustafa
    Sustainability of irrigation systems is crucially important for both economical and efficient usage of natural water sources. Irrigation system efficiency could be negatively affected by some natural flora such as micro (Arthrospira maxima) and macro (Cladophora sp.) algae. In this study, efficiency of UV-C radiation, which has been proven effectiveness in demolishing of bacteria and microbes in medicine, for micro and macro algae. Our study was performed under laboratory conditions and was carried out in two main phases. In the first phase, spectral absorbance curves were established for micro and macro algae, the greatest absorbance value was determined in UV region (300 nm to 450 nm). In the second phase, to analyze the growth of algae species depending on UV-C illumination, micro algae within three different basins with the same cross-sectional area and different water depths (D1 :12.5 cm, D2:25 cm, D3:45cm) were exposed to UV-C radiation for different durations (2, 4, 6. 8 and 16 s). The maximum inhibition on the growth rate of A. maxima was observed in 16 s UV-C radiation treatment groups of D1 and D2 basins. Since Cladophora sp. macro algae are aquatic weeds floating over the water surface, they were exposed to UV-C radiation similar to micro algae only in D1 basin. The greatest reduction rate in biomass values of Cladophora sp. was observed in 16 s UV-C exposed groups. The experimental findings showed that UV-C radiation could be used to reduce growth of micro and macro algae. It was concluded based on present findings that UV-C radiation could reliably be used for efficient water use in open or dosed irrigation systems. (C) 2019 Elsevier B.V. All rights reserved.
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    Pippard relations close to the melting point in the premelting region of hexadecane
    (2012) Yurtseven, Hamit; Tilki, Özcan; Kurt, Mustafa
    We examine here the validity of the Pippard relations close to the melting point in the premelting region of hexadecane. For this verification, we analyze the observed data for the thermal expansivity ? p obtained for various pressures at constant temperatures of 302 and 325 K in this system. By calculating the isothermal compressibility T and the specific heat C p in the same pressure region of the premelting region of hexadecane, we obtain that C p varies linearly with ? p and also that ? p varies linearly with T for this system. This indicat es that some molecular organic compounds, such as solid hexadecane studied here, can exhibit -phase transitions prior to melting which are expected to verify the Pippard relations. © 2012 Hamit Yurtseven et al.
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    Refractive index and extinction coefficient determination of an absorbing thin film by using the continuous wavelet transform method
    (Optical Soc Amer, 2008) Coskun, Emre; Sel, Kivanc; Ozder, Serhat; Kurt, Mustafa
    We present the continuous wavelet transform (CWT) method for determining the dispersion curves of the refractive index and extinction coefficient of absorbing thin films by using the transmittance spectrum in the visible and near infrared regions at room temperature. The CWT method is performed on the transmittance spectrum of an a - Si1-xCx:H film, and the refractive index and extinction coefficient of the film are continuously determined and compared with the results of the envelope and fringe counting methods. Also the noise filter property of the method is depicted on a theoretically generated noisy signal. Finally, the error analyses of the CWT, envelope, and fringe counting methods are performed. (C) 2008 Optical Society of America
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    Temperature Dependence of the Tilt Angle for the Smectic A-Smectic C* Transition in a Mixture of C7-70PDOB Ferroelectric Liquid Crystals near the Tricritical Point
    (Hindawi Ltd, 2012) Kurt, Mustafa; Yurtseven, Hamit
    The temperature dependence of the tilt angle theta is studied in the smectic C* phase near the smectic A-smectic C* tricritical point for a mixture of 70PD0B in the ferroelectric liquid crystal C7 (X = 16.92). The mean-field models with the biquadratic P-2 theta(2) (P is the spontaneous polarization) and P-2 theta(2) + P theta (bilinear) coupling terms in the free energy expansion are used to analyze the experimental data for the tilt angle in this binary mixture. From our analysis, the coefficients given in the free energy expansion of the mean-field models are determined. Our results show that the mean-field theory explains adequately the observed behaviour of the C7-70PD0B mixture near the AC* tricritical point.
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    Uyarlamalı Optik Sistemler İçin Sabit Dereceli H_Sonsuz Alt-Optimal Kontrolcü Geliştirilmesi
    (2021) Erol, Bilal; Kurt, Mustafa; Altıner, İhsan Berk; Yılmaz, Onur; Koç, Celal Tayfur
    Atmosferik türbülans kaynaklı bozulmalar, uzak mesafe görüntüleme, laser ışın demetinin belirli bir hedefte odaklanması gibi uygulamaların performanslarını düşürmektedir. Uyarlamalı optik sistemler (Adaptive Optics-AO), türbülans etkisinin azaltılması ve böylece ışınlardaki bozulmaları düzelterek optik sistemlerin etkinliğini arttırmak için kullanılmaktadır. Atmosfer, yapısı gereği içerisinde çeşitli nem ve sıcaklık değerlerine sahip boyutları birbirinden farklı hava baloncukları barındırır. Işın demeti atmosfer içinde ilerlemesiyle kırılım indeksi olarak adlandırılan farklı yapılara sahip değişkenler tarafından kırılıma uğrar. Bu tür sistemler temel olarak görüntü kalitesini arttırmak için büyük çaptaki gözlem teleskoplarında, hızlı hareket eden sistemlerin takibi için hedef takip sistemlerinde ve özellikle haberleşme sistemlerindeki lazer demetinin dağınımını gerçek zamanlı olarak kontrol etmekte kullanılmaktadır. AO sistemlerin temel bileşenleri deforme edilebilir ayna (DM), dalga cephesi algılayıcısı (WFS) ve kontrol birimidir. Sistemin temel çalışma prensibi, algılama, hesaplama ve etkinleştirme biçimindedir. İlk olarak dalga cephesi DM tarafından karşılanır ve dalga cephesindeki bozulma algılayıcı ile tespit edilir. Daha sonra kontrol birimi de dalga cephesindeki hatayı giderecek şekilde deforme edilebilir aynayı sürer ve aynadan yansıyan dalganın cephesi düzeltilmiş olur. Bu tür sistemlerdeki olması gereken kontrol stratejisi ayna yüzey şeklinin uygun tayini üzerinedir. Bu çalışmanın amacı, uyarlamalı optik sistemlerin ana bileşeni olan deforme edilebilen ayna için model bazlı bir kontrol tasarımına gidilerek optik bozulma etkilerinin en aza indirgenmesidir. Bu amaç doğrultusunda tasarlanan ilk kontrolcü, sabit dereceli HSonsuz alt-optimal kontrolücüdür. Standart optimal HSonsuz kontrolcü derecesinin en az sistem derecesinde olması gerekmektedir. Literatürde bu tipteki kontrolcülere tam dereceli kontrolcüler denmektedir. Bu tasarım kısıtından dolayı nihai kapalı çevrim sistemin derecesi bir kat daha artmaktadır. Uzay ve havacılık uygulamalarındaki mühendisler, yüksek dereceli sistemlerin, parametrelerinde olabilecek değişimlere karşı yüksek duyarlılığa sahip olmalarından ötürü, tam dereceli kontrolcüleri kullanmaktan kaçınmaktadırlar. Ayrıca tam-dereceli kontrolcüleri gömülü sistemler ile gerçeklemek oldukça güçtür. Bundan dolayı, bilgisayar destekli sistemlerin kontrolünde ortaya çıkan önemli problemlerden biri sabit dereceli kontrolcülerin tasarımıdır. Sabit dereceli kontrolcü tasarımındaki en büyük güçlük de ifade edilen bölgenin konveks olmayan bir formda olmasıdır. Bunun üstesinden gelmek ve önem arz eden frekans aralığına odaklanmak amacıyla model indirgeme tekniklerine (FWBMR) başvurulmuştur. Böylece herhangi bir ağırlıklandırma filtresinin sebep olacağı yüksek dereceden sistemle ile uğraşmak yerine, hedeflenen frekans bölgesinde düşük dereceden kontrolcü gerçekleştirebilecektir. Ağırlıklandırma filtrelerin kullanımı ile tasarlanan HSonsuz kontrolcü hem çok yüksek dereceden olmakta hem de bu noktalara kontrolcünün odaklanması sağlanmaktadır, halbuki FWBMR sayesinde bu bant genişliğinde elde edilen sistem ile direkt bu noktalara odaklanılmaktadır.