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Discrete singular convolution method for acoustic transmission lines
(Springer Singapore Pte Ltd, 2020) Kara, Murat; Seçgin, Abdullah; Baygün, Tuba
Discrete singular convolution (DSC) algorithm is an accurate dynamic analysis method for single structures. However, vibration analysis of connected structures via the DSC method is limited to step beams and plates. This paper extends the applicability of the DSC method in handling acoustic transmission lines composed of several duct elements with different diameter ratios. Connections of elements are handled by setting up continuity equations at geometric discontinuities. Conformity of DSC equations at these connections is carried out using Taylor series expansion. In this study, natural frequencies, mode shapes and power transmission coefficients of acoustic transmission lines are performed to test the proposed DSC implementation. Power transmission coefficients are obtained through the two-load method using the data provided by the DSC approach. The results are compared with finite element method and analytical solutions (if applicable), and the analytical transfer matrix method is also used for validating the power transmission coefficients. This paper shows that the DSC method is accurate and reliable, and so applicable for acoustic transmission line analysis.
Discrete singular convolution method for modelling of waveguide interaction of beam-type structures with impedance boundaries
(ELSEVIER SCI LTD, 2021) Kara, Murat; Seçgin, Abdullah
Discrete Singular Convolution (DSC) is an accurate local/global mathematical method for the vibration and acoustic analysis of individual continuous structures. In recent years, successful applications of the DSC method for handling connected structures have been performed. However, the studies are very limited and applicable only for common basic boundary conditions such as the pinned, clamped or free boundaries. This study extends the applicability of the DSC method to waveguide interactions of connected structures with the mechanical impedance boundaries. For this purpose, vibration analyses of structures composed of beams forming I-, L- and Ttype structures are performed via the DSC. Taylor series expansion is utilized to implement the mechanical impedance boundary conditions. The structural models support the longitudinal and bending waveguides and related interactions. Natural frequencies and vibration displacement responses to a point force excitation are predicted via the proposed methodology. The results are validated by finite element and/or analytical solutions. It has been shown that the DSC method can be reliably applied for structures exhibiting waveguide interactions with impedance boundaries.
Discrete singular convolution–polynomial chaos expansion method for free vibration analysis of non-uniform uncertain beams
(SAGE Publications Inc., 2021) Seçgin, Abdullah; Kara, Murat; Ferguson, Neil
This article enhances the discrete singular convolution method for free vibration analysis of non-uniform thin beams with variability in their geometrical and material properties such as thickness, specific volume (inverse of density) and Young’s modulus. The discrete singular convolution method solves the differential equation of motion of a structure with a high accuracy using a small number of discretisation points. The method uses polynomial chaos expansion to express these variabilities simulating uncertainty in a closed form. Non-uniformity is locally provided by changing the cross section and Young’s modulus of the beam along its length. In this context, firstly natural frequencies of deterministic uniform and non-uniform beams are predicted via the discrete singular convolution. These results are compared with finite element calculations and analytical solutions (if available) for the purpose of verification. Next, the uncertainty of the beam because of geometrical and material variabilities is modelled in a global manner by polynomial chaos expansion to predict probability distribution functions of the natural frequencies. Monte Carlo simulations are then performed for validation purpose. Results show that the proposed algorithm of the discrete singular convolution with polynomial chaos expansion is very accurate and also efficient, regarding computation cost, in handling non-uniform beams having material and geometrical variabilities. Therefore, it promises that it can be reliably applied to more complex structures having uncertain parameters.
Ereğli Kömür Havzası ve Cumhuriyet Dönemi şekillenişi
(Bolu Abant İzzet Baysal Üniversitesi, 2009) Kara, Murat; Ocak, Ahmet
Ereğli Kömür Havzası, kömürün bulunuşundan günümüze değin önemini hep korumuştur. 1829 yılında kömürün Zonguldak Ereğli'de bulunmasıyla başlayan bu süreç, gerek kömürün işletilmesi, gerekse kömürün iç ve dış piyasalara satışı sırasında da devam etmiştir. Osmanlı Devleti zamanında önce Padişah İdaresi'nce işletilen havzada, yerli ve yabancı sermayedarlar aracılığıyla kömür üretimi yapılmıştır. Ancak bunda istenen üretim hedefine ulaşılamamıştır. 1867 yılında Dilaver Paşa isimli Nizamname uygulamaya konarak ocaklarda zorunlu çalışma dediğimiz ?mükellefiyet? uygulaması yapılmış, fakat yine de hedeflenen sonuca ulaşılamamıştır. Bahriye Nezareti İdaresi zamanında ise üretilen kömürün % 40'nın istenen şekilde satışına izin verilmesi üzerine havzaya hem sermaye akını olmuş hem de kömür üretimi artmıştır. Fakat yabancı sermaye kömür havzasında her zaman kendi çıkarına göre hareket ettiği için arzulanan kömür üretimi elde edilememiştir. Meşrutiyet devri, Harp ve Mütareke yıllarının olumsuz durumundan kömür üretimi de etkilenmiştir.Ereğli Kömür Havzası böyle bir durumda Milli Hükümet ve Cumhuriyet dönemine geçmiştir. Milli Hükümet'in yerli kaynaklar konusundaki tutumu sonucu havzada çok önemli çalışmalar yapılmıştır. İlk önce özel teşebbüsün teşvik edilmesiyle başlayan bu süreç, özel teşebbüsün ağır sanayi konusunda yetersiz kalması sonucu bizzat devlet eliyle yapılmıştır. Gerek İzmir İktisat Kongresi, gerek İş Bankasının havzaya girmesi, gerekse Teşvik-i Sanayi Kanunu sonrası havza büyük bir değişim yaşamıştır. Dolayısıyla yerli ve yabancı sermayedarlar arasındaki fark ortaya çıkmıştır. 1930-1940 arası uygulanan kalkınma planlarıyla havza büyük bir değişim yaşamıştır. Ancak II.Dünya savaşı nedeniyle bu gelişim yavaşlamıştır.Ereğli Kömür Havzası denince akla gelen bir başka önemli konu, Kömür havzasının devletleştirilmesi sonucu II.Dünya savaşının da olumsuz etkilerinden dolayı ülke ekonomisi için önemli olan kömür üretimini arttırmak amacıyla Milli Korunma Kanunu'na dayanılarak uygulamaya konan ?Ücretli İş Mükellefiyeti?dir. 1940-1947 yılları arasını kapsayan bu dönemde havza köylüleri maden ocaklarında zor şartlar altında çalıştırılmışlardır. Nitekim tez çalışmamızın bu bölümünde mükellef döneminde ocakta çalışmış olan kişilerle görüşmeler yapılarak uygulama hakkında bilgiler toplanmıştır. Bu görüşmeler yapılırken ?sözlü tarih? yöntemi kullanılmıştır. Hazırlamış olduğumuz sorular ?mükellef işçilere? yöneltilmiş ve sonrasında analizi yapılmıştır. Görüşülen kişilerin 80 yaşın üzerinde olması hem konunun önemini hem de çalışmanın zorluğunu ifade etmektedir. Ortaya çıkan sonuç ise son derece yararlı olmuştur. Çünkü ülkemizdeki ortalama yaş durumu göz önüne alınırsa maden ocaklarında çalışıp 80 yaşını aşmış sağlıklı insanın bulunması gerçekten zor bir durumdur.Anahtar kelimeler: Ereğli, Kömür, Dilaver Paşa, Milli Korunma Kanunu, İş Mükellefiyeti, Sözlü Tarih.
Experimental determination of sound transmission loss of some wood species
(Kastamonu Univ, 2020) Çavuş, Vedat; Kara, Murat
Aim of study: To determine the sound transmission losses of 16 different wood species with the different density in the range of 100-1000 Hz frequencies, and the relationship between density and transmission loss was. Material and methods: In this study sound transmission loss values of Ash (Fraxinus excelsior), Acacia (Robinia pseudoacacia L.), Beech (Betula pendula), Black pine (Pinus nigra), Black poplar (Populus nigra), Canadian poplar (Populus x euramaricana), Chestnut (Castanea sativa Mill.), Cypress (Cupressus sempervirens), Oriental beech (Fagus orientalis Lips,) Eucalyptus C. (E, camaldulensis Dehnh), Eucalyptus G. (Eucalyptus grandis), Juniper (Juniperus excelsa), Plane (Platanus orientalis L.), Scotch pine (Pinus sylvefris L), Turkish Red pine (Pinus brutia Ten) and White Oak (Quercus alba) wood specimens were determined by using the impedance tube kit. Main results: Sound transmission loss is observed in lower density wood material species with the increasing frequency. However, a clear relationship has not been established between the mean sound transmission loss and density. Highlights: It is important to determine the frequency-related acoustic performance parameters of the wood material and to its relationship with density.
A higher order statistical moment based approach for the distribution of eigenvalues of beams with variable cracked depth
(Academic Press Ltd- Elsevier Science Ltd, 2021) Kara, Murat
Statistical moment analysis proved its accuracy on the determination of mean and variance of free and forced vibration response for the structures having normally distributed global input and output parameters. Apart from the mean and variance, higher order standardized central statistical moments (CSMs) i.e., skewness and kurtosis, must also be evaluated for the nonnormal distributions to obtain probability density function of random variables. In this study, statistical moment analysis is enhanced to calculate higher order CSMs in order to evaluate the distribution of eigenvalues of beams. The method is applied for intact and cracked beams having variable parameters. For the intact beam case, higher order CSMs of eigenvalues are determined corresponding to the normally distributed global variable parameter, i.e., Young's modulus. The latter application of the method is on the cracked beams having a nonnormal variable local parameter, i.e., crack depth. For this case, the method is tested by modelling the crack depth by two different distributions. In this regard, firstly, expressions of CSMs are analytically derived for the mathematical operations (summation and multiplication) of two statistical variables. Then, these expressions are fed to mathematical model (constructed via Rayleigh Ritz method) of cracked beams to calculate statistical moments of eigenvalues. Next, distributions of the eigenvalues corresponding to the variable cracked depth are obtained by utilizing CMSs in Pearson distribution. The results are compared with Monte Carlo simulation and present unique advantages in the sense of computational cost for the structures having variable parameters. (C) 2021 Elsevier Ltd. All rights reserved.
A hybrid methodology for the frequency response function variability due to joint uncertainty
(Academic Press Ltd- Elsevier Science Ltd, 2023) Kara, Murat; Ferguson, N. S.
In vibroacoustic engineering, the most probable cause of dynamic uncertainty are the joints since it is not easy to strictly control the properties of manufactured joints. Although uncertainty in joints is localized in a complex structure, it may affect the dynamic response of the whole structure especially at higher frequencies. Generally, uncertain industrial structures are modelled numerically by FE whereas the uncertainty is modelled by performing Monte Carlo Simulations (MCS). These combined approaches are named FE-MCS. Application of FE-MCS to analyse local uncertainty in a complex structure is computationally slow, as FE and MCS requires a high number of elements and sampling, respectively. A possible solution is to introduce a combined hybrid Wave Finite Element and FE (shortly hybrid WFE) model, treating the uniform structures as waveguides joined by a local FE joint representation. Then, Polynomial Chaos Expansion (PCE) can be applied to introduce and model the uncertainty. The methodology is developed herein and tested on two right angled beams forming a L-shaped joint. The joint thickness is assumed to have a uniform distribution as an uncertain parameter. The scattering coefficients and frequency response function for both beams, are selected as the resulting uncertain variables. The results are subsequently verified with FE-MCS simulations using 200 samples and a limited number of ex-periments. It is clearly shown that the methodology introduced is an efficient tool for the structures possessing local uncertainty in terms of computational load as well as producing good frequency response function predictions when compared to both FE-MCS simulations and experimental validation.
Identification of slotted beam parameters for low frequency flow-induced vibration energy harvesting
(Springer Heidelberg, 2023) Bolat, Fevzi Çakmak; Kara, Murat
It is a well-known fact that, the amplitude and frequency of flow-induced vibration are related with the dynamics of the considered structure. In this study, the performance of energy harvesting structure due to flow-induced vibration is examined. In this regard, a thin beam is considered, and dynamics of the beam is changed by creating slots on it. As a result of creating slots, more energy may be harvested from piezoelectric-based energy harvesting generator in lower frequency dynamics since the slotted beam has lower stiffness and hence lower natural frequency and higher vibration amplitude in low frequencies. In the study, firstly, the fundamental natural frequency of an intact beam (beam without slot) is evaluated by finite element (FE) method and is validated by using Rayleigh-Ritz (R-R) method and experiments. Then, since flow-induced vibration is of interest, the amplitude of the experimental excitation force is determined via an inverse approach. Next, FE model for the slotted beam is constructed and natural frequencies are compared with R-R method. After the verification of the natural frequency of intact/slotted beam, the frequency response function is validated. For this purpose, R-R method combined with mode superposition and FE method are utilized. Then, for the intact beam, harvested energy power is also determined by experimental measurements under flow-induced excitation. Finally, number, position, and depth of the slots of a slotted beam are changed in the certain limits and corresponding frequency response functions are determined by using finite element method to obtain more harvested energy in lower frequency dynamics.
Investigation of energy harvesting in composite beams with different lamination angles under dynamic effects
(ELSEVIER SCI LTD, 2021) Bolat, Fevzi Çakmak; Başaran, Sinan; Kara, Murat
In this study, energy harvesting from cantilever composite beams produced at different lamination angles was experimentally investigated. In this regard, three different eight layered laminated composite beams are considered, i.e., {0 degrees, 90 degrees, 0 degrees, 90 degrees}s, {-30 degrees, 60 degrees, -30 degrees, 60 degrees}s and {-45 degrees, 45 degrees, -45 degrees, 45 degrees}s. energy harvest performances were analyzed under different external dynamics inputs by bonding piezoelectric material to the surface of composite beams. Firstly, the composite beam harvesting structure was excited by air-flow. In those experiments, three different types of bluff-body geometry elements were attached to the free end for each of the considered composite beams. In order to determine the maximum power output, different resistors are attached to the piezoelectric material. As a second dynamic input, an electromagnetic actuator operating on the Lorentz principle is used. By using this electromagnetic actuator, the structures are excited by harmonic inputs with different frequencies and frequency-voltage responses were obtained. Besides, vibration amplitudes and voltage outputs were analyzed for both excitation types.
Kalın ve katmanlı kompozit plakaların temel doğal frekansının mekanik özelliklerin küçük değişimlerine duyarlılığı
(2021) Kara, Murat
Kompozit plakaların istenilen özelliklere göre tasarımı genellikle deneme yanılma ile yapılmaktadır. Bu durum eldeedilen nihai tasarım sürecini uzatmaktadır. Dolayısıyla tasarım sırasında istenilen tasarım amaç fonksiyonu üzerinde etkilitasarım parametrelerin belirlenmesi oldukça önemlidir. Bu bağlamda duyarlılık analizi sıklıkla kullanılan yöntemlerdenbirisidir. Bu çalışmada farklı kalınlıklardaki kalın katmanlı kompozit plakaların temel (birinci) doğal frekansınınduyarlılık analizi gerçekleştirilmiştir. Fiber ve fibere dik yöndeki elastisite modülü ve üç yöndeki kayma modülleritasarım parametreleri olarak seçilmiştir. Ardından sonlu elemanlar tabanlı Monte Carlo simülasyonu ile tasarımparametrelerinin kombinasyonuna karşılık gelen doğal frekanslar hesaplanmıştır. Daha sonra duyarlılık analizigerçekleştirmek amacıyla matematiksel bir model oluşturulmuştur. Sonuçta kalınlığa bağlı olarak temel doğal frekansınduyarlılığı elde edilmiştir.
Sensitivity analysis of laminated composite plates with different orientations in low to high order modes
(Iop Publishing Ltd, 2021) Kara, Murat; Güler, Serkan; Seçgin, Abdullah
Laminated composite plates are utilized due to their high strength/weight ratios. Since such structures are light and have less stiffness, their natural frequencies are lower than usual isotropic structures. Therefore, their behaviours in higher order modes are of interest. On the contrary, sensitivity analysis of vibrating structures is generally performed for lower order modes. In this study, sensitivity analysis of symmetrical/anti-symmetrical/asymmetrical laminated composite plates is performed in low to high order modes. In this regard, angular orientation, Young's modulus, shear modulus, Poisson's ratio and density of the plate are selected as design parameters whereas natural frequencies are selected as design objective functions. Discrete singular convolution method is used as solver due to its high computational capability. Although some other conclusions are drawn, it can mainly be concluded that, the natural frequencies are very sensitive to small differences in Poisson ratio for orientation angles of considered plates.
Stochastic prediction of natural frequencies of laminated composite beams by using a high-order statistical moment based approach
(Elsevier Science Ltd, 2022) Kara, Murat; Seçgin, Abdullah; Baygün, Tuba; Akyol, Çağrı Gökhan
Statistical Moment (SM) based modelling is a quite straightforward approach in stochastic modelling of uncertain structures. However, the method still has deficiencies including determination of SMs of natural frequencies of vibratory structures, and it has not been tested yet for realistic structures. This study aims such verification by employing high-degree statistical moments in stochastic equations. In this respect, SM approach is applied for two different uncertainty cases. In the first case, uncertain parameters are experimentally reproduced from the batch of laminated composite beams. Then, those uncertainties are fed to SM equations used in finite element model to obtain descriptive statistical quantities (mean, variance, skewness, and kurtosis) of stochastic natural frequencies. Next, Pearson model is utilized to obtain probability density function of the natural frequency by using standardized SMs. Beside this, uncertain fundamental natural frequency of fifty samples of composite beams is measured by experimental modal tests. All SM based predictions and modal test results are also compared with numerical Monte Carlo Simulations. The latter case examines composite beams having non normal uncertain thickness. Since the results are in good harmony with each other, it is concluded that high order SM based approach may effectively be used in uncertainty modelling of realistic structures.
A two-stage polynomial chaos expansion application for bound estimation of uncertain FRFs
(Academic Press Ltd- Elsevier Science Ltd, 2023) Kara, Murat; Ferguson, Neil S.
Polynomial Chaos Expansion (PCE) is a method for analysing uncertain vibratory structures with lower computational effort. It may simply be described as a curve fitting method with orthogonal basis terms, where the polynomial type, dimension and order are predefined for the uncertain responses. However, the polynomial order in PCE must be very high to accurately estimate statistical moments of the frequency response function in resonance regions of lightly damped and uncertain structures. To solve this issue different transformation techniques are reported in the literature, where implementations of PCE produce higher accuracy with a lower order polynomial. However, these transformations lose the attraction for using PCE, since they require some additional mathematical operations and, mostly, they present high accuracy if the higher orders of polynomials are again of interest. In this study, an efficient approach is presented for the upper bound estimation of the uncertain frequency response functions (FRFs) via PCE with lower order terms without performing any transformation. Rather than one-stage application of PCE for the desired response of an uncertain problem, the approach comprises a two-stage application of the classical PCE, i.e. first for the natural frequencies and then for the FRF calculations. As an example application of the approach, a thin beam for two different uncertainty cases is considered, namely local and global uncertainty. The local and global input uncertainties are generated by variability of lumped masses added at the boundary and Young's modulus, respectively. The FRF bounds are compared with extensive experimental and numerical Monte Carlo simulations, showing that low order polynomials are sufficient to calculate the bounds accurately with the technique described.
The value of interleukin-12B (p40) gene promoter polymorphism in patients with schizophrenia in a region of East Turkey
(Wiley-Blackwell, 2008) Özbey, Ülkü; Tuğ, Esra; Kara, Murat; Namlı, Mustafa
Aims: It has been hypothesized that the activation of the immune system may be involved in the neuropathological changes occurring in the central nervous system of schizophrenic patients. Cytokines play a key role in the activation of the immune system. Moreover, they strongly influence the dopaminergic, noradrenergic and serotonergic neurotransmission. To the best of our knowledge, in schizophrenic patients, plasma levels of interleukin (IL)-12 were investigated only in one study, where deregulation of IL-12 was determined. However, genotypical variations of the IL-12B (p40) gene have not been investigated for schizophrenic patients yet. Therefore, in the present study, we aimed to examine polymorphic variants of IL-12B (p40) gene promoter region in patients with schizophrenia in a population of the Elazig Region of East Anatolia, Turkey. Methods: One hundred Turkish patients diagnosed with schizophrenia based on the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), and 116 healthy control subjects participated in the present study. The genotype characteristics were determined by polymerase chain reaction-based restriction fragment length polymorphism method using DNA extracted from peripheral blood. Results: Significant differences in both the genotype and allele frequencies were found between schizophrenia patients and control groups (P < 0.01). Conclusions: These findings may support the hypothesis that activation of the inflammatory response system and in particular, of Th-1 cells, is involved in the pathophysiology of schizophrenia. We think that this study is the first trial associated with IL-12 cytokine at the molecular genetic level on immune mechanisms for neuropsychiatric disorders including schizophrenia, and this perspective and the role of the cytokines in the pathogenesis of schizophrenia may constitute a reasonable target for the present and future treatment strategies and prognosis.
THE VALUE OF INTERLEUKIN-12B (P40) GENE PROMOTER POLYMORPHISM IN PATIENTS WITH SCHIZOPHRENIA IN A REGION OF EAST TURKEY
(Wiley-Blackwell, 2009) Ozbey, Ulku; Tug, Esra; Kara, Murat; Namli, Mustafa

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