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Öğe Acoustic beam splitting in a sonic crystal around a directional band gap(Iop Publishing Ltd, 2013) Cicek, Ahmet; Kaya, Olgun Adem; Ulug, BulentBeam splitting upon refraction in a triangular sonic crystal composed of aluminum cylinders in air is experimentally and numerically demonstrated to occur due to finite source size, which facilitates circumvention of a directional band gap. Experiments reveal that two distinct beams emerge at crystal output, in agreement with the numerical results obtained through the finite-element method. Beam splitting occurs at sufficiently-small source sizes comparable to lattice periodicity determined by the spatial gap width in reciprocal space. Split beams propagate in equal amplitude, whereas beam splitting is destructed for oblique incidence above a critical incidence angle.Öğe Acoustic Mach-Zehnder interferometer utilizing self-collimated beams in a two-dimensional phononic crystal(Elsevier Science Sa, 2014) Kaya, Olgun Adem; Cicek, Ahmet; Salman, Aysevil; Ulug, BulentNumerical investigation of a Mach-Zehnder interferometer implemented by steering self-collimated acoustic beams in a two-dimensional phononic crystal is presented. Mirrors of the interferometer are optimized by modifying the radii of the steel cylinders in water so that the working frequencies lie in a band gap. The beam splitters optimized in a similar manner ensure equal splitting of the beams. In the all water case of host liquid, the interferometer operates unidirectionally such that transmission throughonly one of the two output terminals is achieved. Corresponding transmittances are 85.9% and 6.0% for the transmitting and blocked terminals, respectively. The device can be utilized in sensing variations in the weight fraction of ethanol in water in a cell on the path of one of the two split beams. Phase difference accumulated in the sample cell varies linearly with ethanol weight fraction up to 15%. Contrast ratio of the calculated transmittances can be used as a measure of ethanol content in water, as it varies as a cosine function of ethanol weight fraction. (C) 2014 Elsevier B. V. All rights reserved.Öğe Acoustic Michelson interferometer based on a phononic crystal(Aip Publishing, 2023) Durmuslar, Aysevil Salman; Kaya, Olgun Adem; Bicer, Ahmet; Cicek, AhmetA practical and highly sensitive acoustic Michelson interferometer with a small form factor is introduced. It involves two different types of phononic crystals composed of steel rods in water acting as a medium for self-collimated waves and mirrors for the reference and sample beams, as well as a beam splitter formed by modified scatterers arranged diagonally. Finite-element method simulations are employed to demonstrate its operation around 200 kHz. Equifrequency contour analysis reveals self-collimation of ultrasonic waves between 190 and 210 kHz. Introduction of the beam splitter and mirror phononic crystals is not detrimental to self-collimation where outgoing waves from the two interferometer arms interfere such that the output intensity varies in a cosine squared manner. Consequently, maximum sensitivity is achieved when the movable mirror displacement is either zero or half of the interferometer phononic crystal period. On small intervals in these ranges, micrometer-scale displacement resolution is achievable, as the output intensity drops by 0.2% per micrometer. Thus, displacements smaller than a percent of the wavelength are easily resolvable. Nanoscale resolution can be obtained with a scaled down interferometer design. Moreover, application to liquid concentration sensing by considering ethanol-water binary mixture is demonstrated. A percent increase in weight fraction of ethanol up to 10% in the mixture leads to an intensity drop as high as 2%. Thus, significantly higher sensitivities compared to sensing schemes based on resonance frequency shift are attainable. The proposed approach can be adapted for surface acoustic waves in strain measurement or biosensing.Öğe Acoustic sorting of airborne particles by a phononic crystal waveguide(Elsevier, 2022) Korozlu, Nurettin; Bicer, Ahmet; Sayarcan, Done; Kaya, Olgun Adem; Cicek, AhmetA two-dimensional phononic crystal linear defect waveguide is utilized for size-based sorting of millimeter-sized solid particles in the air through acoustic radiation force. The waveguide channels ultrasonic waves at 20 kHz, as calculated through Finite-Element Method simulations. Spherical solid particles released from rest at the top of the vertically aligned waveguide experience the combined effect of the acoustic radiation, gravity, and drag forces. When the particles are released from the symmetry plane of the waveguide, they follow straight paths where the ones with radii smaller than a threshold value are trapped at the waveguide nodal planes, whereas larger particles are let pass through. This requires input sound pressure levels between 173 dB and 177 dB. Moreover, such particles can also be differentiated with respect to density. Alternatively, the release of particles with a slight offset from the symmetry center induces unbalanced acoustic radiation potential, and thus uneven radiation force, resulting in the initiation of horizontal displacement whose extent depends on particle radius. Thus, both simulation results and experimental findings suggest that this scheme can be employed in size-based particle separation. Sorting of spherical glass particles with 0.5 mm and 1.0 mm radii are experimentally demonstrated for low ultrasonic transducer acoustic power output up to 90 W. The proposed approach can be utilized in applications where contact-free separation of airborne particles is required.Öğe Acoustic tamm states of three-dimensional solid-fluid phononic crystals(Acoustıcal soc amer amer ınst physıcs, ste 1 no 1, 2 huntıngton quadrangle, melvılle, ny 11747-4502 usa, 2018) Korozlu, Nurettin; Kaya, Olgun Adem; Cicek, Ahmet; Ulug, BulentIn this work, the existence and propagation of acoustic Tamm states at the interface of air and a face-centered cubic solid-fluid phononic crystal composed of spherical air voids interconnected by cylindrical air channels are demonstrated. Supercell band structure computations via the finite element method reveal surface bands for Tamm states on (100), (110), and (111) surfaces of the phononic crystal. The states decay sharply into the phononic crystal so that only a two-row slab is sufficient to guide them over the respective surfaces without leakage, as confirmed by finite element simulations. In addition, surface wave propagation along the [10] direction of the (100) surface is experimentally demonstrated. Ability to confine the Tamm states in all three dimensions is a key aspect in designing few-layer-thick acoustic circuits. Low material filling fraction of the phononic crystal could be leveraged to realize lightweight all-acoustic systems where either bulk or surface states can be incorporated. (C) 2018 Acoustical Society of America.Öğe Acoustic Tamm states of three-dimensional solid-fluid phononic crystals(Acoustical Soc Amer Amer Inst Physics, 2018) Korozlu, Nurettin; Kaya, Olgun Adem; Cicek, Ahmet; Ulug, BulentIn this work, the existence and propagation of acoustic Tamm states at the interface of air and a face-centered cubic solid-fluid phononic crystal composed of spherical air voids interconnected by cylindrical air channels are demonstrated. Supercell band structure computations via the finite element method reveal surface bands for Tamm states on (100), (110), and (111) surfaces of the phononic crystal. The states decay sharply into the phononic crystal so that only a two-row slab is sufficient to guide them over the respective surfaces without leakage, as confirmed by finite element simulations. In addition, surface wave propagation along the [10] direction of the (100) surface is experimentally demonstrated. Ability to confine the Tamm states in all three dimensions is a key aspect in designing few-layer-thick acoustic circuits. Low material filling fraction of the phononic crystal could be leveraged to realize lightweight all-acoustic systems where either bulk or surface states can be incorporated. (C) 2018 Acoustical Society of America.Öğe Acoustic waveguiding by pliable conduits with axial cross sections as linear waveguides in two-dimensional sonic crystals(Acoustical Soc Amer Amer Inst Physics, 2013) Cicek, Ahmet; Kaya, Olgun Adem; Ulug, BulentPliable conduits composed of periodically arranged concentric aluminum tori in air, with their axial cross sections acting as linear waveguides in two-dimensional sonic crystals, are numerically shown to guide acoustic waves in three dimensions in a flexible manner. Waveguide band structures are obtained by exploiting axial symmetry in a super-cell approach through two-dimensional finite-element simulations under the periodic boundary conditions. One isolated band having a bandwidth of 19.66% or 10.10% is observed for each guide, whose cross section is either in square or triangular geometry, respectively. Corresponding mode profiles indicate efficient guiding, as the acoustic energy is mainly concentrated in the hollow-core region of the guides. Transmittance spectra calculated through finite-element simulations are in agreement with the computed guiding bands. Transmittance along the waveguides with square and triangular axial cross sections around mid-band frequencies of their guiding bands varies slightly from -6.05 and -6.65 dB to -5.98 and -8.86 dB, respectively, as the guide length is increased from 10 to 200 periods. Efficient guiding across the smooth bends over circular arcs up to 90 deg is also demonstrated through three-dimensional finite-element method simulations. (C) 2013 Acoustical Society of America.Öğe Acoustophoretic separation of airborne millimeter-size particles by a Fresnel lens(Nature Portfolio, 2017) Cicek, Ahmet; Korozlu, Nurettin; Kaya, Olgun Adem; Ulug, BulentWe numerically demonstrate acoustophoretic separation of spherical solid particles in air by means of an acoustic Fresnel lens. Beside gravitational and drag forces, freely-falling millimeter-size particles experience large acoustic radiation forces around the focus of the lens, where interplay of forces lead to differentiation of particle trajectories with respect to either size or material properties. Due to the strong acoustic field at the focus, radiation force can divert particles with source intensities significantly smaller than those required for acoustic levitation in a standing field. When the lens is designed to have a focal length of 100 mm at 25 kHz, finite-element method simulations reveal a sharp focus with a full-width at half-maximum of 0.5 wavelenghts and a field enhancement of 18 dB. Through numerical calculation of forces and simulation of particle trajectories, we demonstrate size-based separation of acrylic particles at a source sound pressure level of 153 dB such that particles with diameters larger than 0.5 mm are admitted into the central hole, whereas smaller particles are rejected. Besides, efficient separation of particles with similar acoustic properties such as polyethylene, polystyrene and acrylic particles of the same size is also demonstrated.Öğe Çeşitli geometrilere sahip akustik kaynakların lineer ortamda oluşturdukları basınç alanlarının incelenmesi(İnönü Üniversitesi, 1998) Kaya, Olgun AdemIV ÖZET: Bu çalışmada çeşitli geometrilere sahip akustik kaynakların, akustik basınç alanları incelenmiştir. Dikdörtgen kaynak model olarak seçilmiş, alan yapısı kare ve dairesel kaynakla karşılaştırılmıştır. Dikdörtgen kaynak için matemetiksel bir model önerilerek, elde edilen sonuçlar eşit alanlı kare ve dairesel kaynak için elde edilen akustik alan yapılan ile karşılaştırılmıştır. Önerilen modelin literatür değerleri ile uyumlu sonuçlar verdiği gözlenmiştir. Daha sonraki aşamalarda yapılabilecek ek çalışmalar tartışılmıştır.Öğe Determination of concentration of ethanol in water by a linear waveguide in a 2-dimensional phononic crystal slab(Elsevier Science Sa, 2014) Salman, Aysevil; Kaya, Olgun Adem; Cicek, AhmetNumerical investigation of a linear defect waveguide in a two-dimensional phononic crystal slab of water cylinders in mercury host to sense the variation of ethanol concentration in a mixture with water is carried out. Waveguide geometry is optimized by varying the waveguide core width and introducing scatterers into the core to obtain an isolated defect band within the bandgap, as close to the gap center and as narrow as possible, in order to increase sensing ability. Transmission results calculated through three-dimensional steady-state finite-element method simulations are consistent with the position and the width of the defect band obtained by band structure computations, as a function of ethanol concentration. The band center varies linearly with ethanol concentration up to 15%, where it blue-shifts with increasing concentration at a rate of approximately 480 Hz per percent variation. The bandwidth also exhibits linear variation up to significantly smaller concentrations, whereas the values calculated through the transmission spectra are considerably smaller than those obtained by band structure computations. (C) 2014 Elsevier B.V. All rights reserved.Öğe Eksenel simetrik akustik dalga kılavuzlarının tasarımı ve sonlu elamanlar yöntemi ile üç boyutlu benzetimi(2012) Kaya, Olgun Adem; Çiçek, Ahmet; Yılmaz, Mükremin[Abstract Not Available]Öğe Evanescent coupling between surface and linear-defect guided modes in phononic crystals(Iop Publishing Ltd, 2016) Cicek, Ahmet; Salman, Aysevil; Kaya, Olgun Adem; Ulug, BulentEvanescent coupling between surface and linear-defect waveguide modes in a two-dimensional phononic crystal of steel cylinders in air is numerically demonstrated. When the ratio of scatterer radii to the lattice constant is set to 0.47 in the square phononic crystal, the two types of modes start interacting if there is one-row separation between the surface and waveguide. Supercell band structure computations through the Finite Element Method suggest that the waveguide band is displaced significantly, whereas the surface band remains almost intact when the waveguide and surface are in close proximity. The two resultant hybrid bands are such that the coupling length, which varies between 8 and 22 periods, initially changes linearly with frequency, while a much sharper variation is observed towards the top of the lower hybrid band. Such small values facilitate the design of compact devices based on heterogeneous coupling. Finite-element simulations demonstrate bilateral coupling behaviour, where waves incident from either the surface or waveguide can efficiently couple to the other side. The coupling lengths calculated from simulation results are in agreement with the values predicted from the supercell band structure. The possible utilisation of the coupling scheme in sensing applications, especially in acoustic Doppler velocimetry, is discussed.Öğe Focusing with two-dimensional angular-symmetric circular acoustic lenses(Pleiades Publishing Inc, 2011) Kaya, Olgun Adem; Cicek, Ahmet; Ulug, BulentFocusing properties of an acoustic lens based on a modified triangular sonic crystal slab whose columns are aligned on concentric arcs of equal radial distance are investigated. Capability of focusing normally-incident plane waves is demonstrated by means of Finite Element Method. Focusing mechanisms are discussed on the basis of band structures and equifrequency contours considering a model where triangular lattice is elongated along IK direction. Focusing behavior of the proposed lens is argued to arise from negative refractions at the air-lens interfaces accompanied by index guiding in its interiors. Wavelength-order confinement in the transverse direction is observed. Double focusing is attributed to geometrical effects and contribution of self guiding is discussed. Possibility of occurrence of birefraction at the input face of the lens together with positive refraction at the output face is also discussed.Öğe Frequency-controlled wave focusing by a sonic crystal lens(Elsevier Sci Ltd, 2009) Alagoz, Serkan; Kaya, Olgun Adem; Alagoz, Baris BaykantIn this study, the frequency dependence of the focalization point was investigated for a sonic crystal lens with a triangular lattice configuration. Theoretical and experimental study results showed that focalization point location of the sonic crystal lens with a triangular lattice configuration depended on the frequency of the wave source in the second frequency band. This property of the sonic crystal lens enables shifting of the focalization point location by means of the frequency of a single acoustic source, and it can find application in technologies based on acoustic wave focusing. (C) 2009 Elsevier Ltd. All rights reserved.Öğe Gas sensing through evanescent coupling of spoof surface acoustic waves(Elsevier Science Sa, 2019) Cicek, Ahmet; Arslan, Yasin; Trak, Digdem; Okay, Fatih Can; Kaya, Olgun Adem; Korozlu, Nurettin; Ulug, BulentAn ultrasonic gas sensor based on evanescent coupling of spoof surface acoustic waves between two surface phononic crystals containing trapezoidal grooves on rigid slabs is theoretically and experimentally demonstrated. Sensing properties for carbon dioxide in dry air at 25 degrees C and 760 Torr are investigated as an example. Band structure analyses reveal two spoof surface acoustic wave bands with opposite parities when the separation of surface phononic crystals is 1.5 times the periodicity of grooves. The beat length varies with frequency and carbon dioxide volume fraction, where the increase of the latter results in red shift of a sharp intense output peak at 59.69 kHz at a rate of 17.70 mHz/ppm and 16.20 mHz/ppm for carbon dioxide volume fractions up to 10,000 ppm, as measured through Finite-Element Method simulations and experiments, respectively. Gas sensing can also be achieved by measuring the output acoustic intensity at constant frequency, which exhibits a steep decrease with carbon dioxide volume fraction up to 2000 ppm.Öğe Guiding airborne sound through surface modes of a two-dimensional phononic crystal(Iop Publishing Ltd, 2015) Cicek, Ahmet; Gungor, Tayyar; Kaya, Olgun Adem; Ulug, BulentExistence and guiding properties of surface modes bound to the interface between a finite two-dimensional phononic crystal and the host medium are experimentally and numerically demonstrated. Surface modes can be observed on both (1 0) and (1 1) surfaces of a square phononic crystal of steel cylinders in air. Numerical investigations of band properties and simulations of mode excitation are carried out through the finite-element method. Excited by the far field of a speaker, existence of surface modes is investigated by recording the sound field in the vicinity of the respective crystal surfaces. Both surface bands of the square phononic crystal depart from bulk bands and extend into the band gap for sufficiently high filling fractions. While such a surface band can be obtained for considerably smaller scatterer radii for the (1 0) surface, significantly higher radii around 0.49 of the lattice constant are required to obtain propagating surface modes on the (1 1) surface. Persistence of the guided surface mode along the (1 0) surface, where it diminishes in a length scale of the lattice constant in the transverse direction is demonstrated. The modes of the (1 1) surface decay faster into the air in the transverse direction. Guided modes on both surfaces propagate in a beating manner where the beat length can be determined by the wave number of the mode.Öğe İki ve üç boyutta nonlineer akustik alan yapılarının nümerik incelenmesi(İnönü Üniversitesi, 2004) Kaya, Olgun AdemÖZET Doktora Tezi İKİ VE ÜÇ BOYUTTA NONLİNEER AKUSTİK ALAN YAPILARININ NÜMERİK İNCELENMESİ Olgun Adem KAYA İnönü Üniversitesi Fen Bilimleri Enstitüsü Fizik Anabilim Dalı 120 + xiii sayfa 2004 Tez Danışmam : Prof. Dr. Ali Şahin Nonlineer akustik alanındaki artan çabalar teknolojik gelişmeleride berabe rinde getirmiştir. Nonlineer etkileri kullanan çok çeşitli medikal aletler klinik uy gulamalarda kullanılmaktadır. Buna rağmen, çoğu aletler alt harmonik bileşenleri kullanmadıkları için, görüntü kalitesi hekimleri memnun edecek düzeyde değildir. Temel neden ise akustik alanların alt harmonik yapıları hakkında yeterli bilgiye sa hip olunmamasındandır. Bu tezin amacı nonlineer akustik alan yapılarını yeterli alt harmonik bileşeni de hesaba katarak anlamak ve açıklığa kavuşturmaktır. Aanenson [1] ve Baker [2] tarafından geliştirilen teorik model iki ve üç bo yutta yüksek genlikli akustik alanlar yaratabilmek için modifiye edilmiştir. Beşinci m harmoniğe kadar her harmonik bileşen için iki ve üç boyutlu alan yapıları sunulmuş tur. Alt harmoniklerin oranlarının açısal ve eksensel görüntü kalitesine etkileri tartışılmıştır. Yapılacak ek çalışmalara kısaca değinilmiştir. ANAHTAR KELİMELER: Akustik Alanlar, Nonlineerlik, Alt harmonik- ler. ivÖğe Impacts of uniaxial elongation on the bandstructures of two-dimensional sonic crystals and associated applications(Elsevier Sci Ltd, 2012) Cicek, Ahmet; Kaya, Olgun Adem; Ulug, BulentInfluences of uniaxial elongation along the [11] direction of triangular and [10] direction of square sonic crystals under the constraint of conserved unit cell area are investigated by examining band structures and equi-frequency contours. Lowest-lying band gap of the triangular lattice observed at high filling fractions diminishes for negative elongation (compression), whereas another band gap develops at lower frequencies whose width reaches appreciable values for moderate elongation. The band gap of the square lattice, which appears at high filling fractions, is modified slightly with elongation. Frequency ranges of the bands, and thus the group velocities along the high-symmetry directions, vary with elongation which may be useful in applications like slow sound propagation. Elongation is observed to modify the equi-frequency contours significantly through reducing the lattice symmetry. The most prominent impact is the transformation of closed contours into open ones, whereas the rest are stretched either along or normal to the elongation axis of the 1st Brillouin Zone. This observation is utilized to implement wide-band all-angle self-collimation and superprism effect, which are demonstrated through Finite-Element computations. (C) 2011 Elsevier Ltd, All rights reserved.Öğe Low-concentration liquid sensing by an acoustic Mach-Zehnder interferometer in a two-dimensional phononic crystal(Iop Publishing Ltd, 2015) Salman, Aysevil; Kaya, Olgun Adem; Cicek, Ahmet; Ulug, BulentMach-Zehnder interferometer formed by liquid-filled linear defect waveguides in a two-dimensional phononic crystal is numerically realized for sensing low concentrations of an analyte. The waveguides in the square phononic crystal of void cylinders in steel, as well as their T branches and sharp bends are utilized to construct interferometer arms. Sensing low concentrations of ethanol on the order of 0.1% in a binary mixture with water is achieved by replacing the contents of a number of waveguide core cells on one arm of the interferometer with the analyte. Computations are carried out through the finite-element method in an approach that takes the solid-liquid interaction at the waveguide core cells into account. Band analyses reveal linear variation of the central frequency of the transmission band within a band gap for ethanol concentrations up to 3.0%. Phase difference due to the imbalance of the sample and reference arms of the interferometer also varies linearly with ethanol concentration, leading in turn to a cosine variation of the Fourier component of the temporal interferometer response at the central input-pulse frequency. The induced phase difference in the investigated configuration becomes a -0.78 pi and -0.65 pi per percent increase of ethanol concentration as calculated from the band-structure and transient data, respectively. This is confirmed by transient finite-element simulations where totally destructive interference occurs for a concentration of approximately 1.5%. The proposed scheme, which can easily be adopted to other binary mixtures, offers a compact implementation requiring small amounts of analyte.Öğe Magnonik kristaller(2015) Atalay, Selçuk; Yurtcan, Mustafa Tolga; Kaya, Olgun Adem; Gencer, Hüseyin; Kaya, Ali Onur; Soykan, Ümmü Gülsüm[Abstract Not Available]
