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        Ozkan,Ocalan 한국전산응용수학회 2014 Journal of applied mathematics & informatics Vol.32 No.5

        In this paper, we investigate the boundedness character, the periodic character and the global behavior of positive solutions of the difference equation xn+1 = pn + xn/xn-1, n = 0,1 ... , where{pn}is a two periodic sequence of nonnegative real numbers and the initial conditions x-1, x0 are arbitrary positive real numbers.

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        Ozkan,Tukel,,Gozde,Turhan,,Tunahan,Yucesan,,Ahmet The Honam Mathematical Society 2019 호남수학학술지 Vol.41 No.2

        Inspired by the problem of finding hyperelastic curves in a Riemannian manifold, we present a study on the variational problem of a hyperelastic curve in Lie group. In a Riemannian manifold, we reorganize the characterization of the hyperelastic curve with appropriate constraints. By using this equilibrium equation, we derive an Euler-Lagrange equation for the hyperelastic energy functional defined in a Lie group G equipped with bi-invariant Riemannian metric. Then, we give a solution of this equation for a null hyperelastic Lie quadratic when Lie group G is SO(3).


        Diphasic Analysis of Growth in Japanese Quail

        Ozkan,,Muhip Asian Australasian Association of Animal Productio 2004 Animal Bioscience Vol.17 No.9

        A line of Japanese quail selected for increased body weight for 15 generations (C) and an unselected control line (K) were used to examine the impact of selection for body weight on the growth curve of Japanese quail. In addition, the effect of sex on the growth curve in each line was also studied, namely females of C (CF), males of C (CM), females of K (KF) and males of K (KM). The monophasic and diphasic growth models were studied for adequacy in describing growth curves of quail in both sexes of the C and K lines. The monophasic function provided almost the same growth rate for both sexes in both lines. However, the growth rates calculated by means of the diphasic function differed between sexes for both lines, except for those calculated for C during the second growth phase. While there were 2-3 days difference between sexes in age at maximum gain in both lines with a monophasic model, the difference between sexes in the age at maximum gain in both lines became greater according to the diphasic model. There were 5 and 7 days difference between sexes in the age at maximum gain in line C for the first and second growth phases, respectively. A difference between sexes of 18 and 11 days in the age at maximum gain for the first and second phases, respectively, was estimated for line K when the diphasic function was fitted. The use of diphasic functions provides more detailed information on growth patterns. The results showed that the use of the diphasic function was better because it provided greater insights into understanding the biology of growth.


        Classification of Grid Connected Transformerless PV Inverters with a Focus on the Leakage Current Characteristics and Extension of Topology Families

        Ozkan,,Ziya,Hava,,Ahmet,M. The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.1

        Grid-connected transformerless photovoltaic (PV) inverters (TPVIs) are increasingly dominating the market due to their higher efficiency, lower cost, lighter weight, and reduced size when compared to their transformer based counterparts. However, due to the lack of galvanic isolation in the low voltage grid interconnections of these inverters, the PV systems become vulnerable to leakage currents flowing through the grounded star point of the distribution transformer, the earth, and the distributed parasitic capacitance of the PV modules. These leakage currents are prohibitive, since they constitute an issue for safety, reliability, protection coordination, electromagnetic compatibility, and module lifetime. This paper investigates a wide range of multi-kW range power rating TPVI topologies and classifies them in terms of their leakage current attributes. This systematic classification places most topologies under a small number of classes with basic leakage current attributes. Thus, understanding and evaluating these topologies becomes an easy task. In addition, based on these observations, new topologies with reduced leakage current characteristics are proposed in this paper. Furthermore, the important efficiency and cost determining characteristics of converters are studied to allow design engineers to include cost and efficiency as deciding factors in selecting a converter topology for PV applications.



        Ozkan,,A.,Sinan,Keskin,,Baki,Cakmak,,Yasar Korean Mathematical Society 2013 대한수학회보 Vol.50 No.2

        The half-inverse spectral problem for an impulsive Sturm-Liouville operator consists in reconstruction of this operator from its spectrum and half of the potential. In this study, the spectrum of the impulsive Sturm-Liouville problem is given and by using the Hochstadt and Lieberman's method we show that if $q(x)$ is prescribed on (0, ${\frac{\pi}{2}}$), then only one spectrum is sufficient to determine $q(x)$ on the interval (0, ${\pi}$) for this problem.

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        Preparation of a fly ash-based geopolymer for removal of a cationic dye: Isothermal, kinetic and thermodynamic studies

        Ozkan,Acisli,Ilker,Acar,Alireza,Khataee 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.83 No.-

        A class Ffly ash-based geopolymer was prepared for the removal of Basic Yellow 2 (BY2) from aqueoussolutions. The geopolymerization process transformed the sphericalfly ash particles into a porous andamorphous polymeric structure, sodium-alumina-silicate hydrate gel. The removal efficiency increasedwith the geopolymer dosage while it decreased with BY2 concentration. Specifically, the efficiency of94.47% was achieved with the geopolymer dosage of 2.0 g L-1. However, further increases resulted in asubstantial reduction, down to 57.76% for 3.0 g L-1. At 293 K for 300 min, the efficiency decreased from84.69 to 64.19% for BY2 concentrations of 10 and 50 mg L-1, respectively. Based on the isothermal, kineticand thermodynamic investigations of the adsorption process, the Langmuir and Temkin models wellcorrelated with the obtained results. The adsorption occurs spontaneously and shows endothermiccharacter. The pseudo-second order and the intra-particle diffusion models are valid for 293 K while theadsorption results well suited with the pseudo-second order for 313 and 323 K. In conclusion, thepreparedfly ash-based geopolymer provided favorable results for the removal of Basic Yellow 2 fromaqueous solutions.

      • Factors Predicting Microinvasion in Ductal Carcinoma in situ

        Ozkan-Gurdal,,Sibel,Cabioglu,,Neslihan,Ozcinar,,Beyza,Muslumanoglu,,Mahmut,Ozmen,,Vahit,Kecer,,Mustafa,Yavuz,,Ekrem,Igci,,Abdullah Asian Pacific Organization for Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.1

        Background: Whether sentinel lymph node biopsy (SLNB) should be performed in patients with pure ductal carcinoma in situ (DCIS) of the breast has been a question of debate over the last decade. The aim of this study was to identify factors associated with microinvasive disease and determine the criteria for performing SLNB in patients with DCIS. Materials and Methods: 125 patients with DCIS who underwent surgery between January 2000 and December 2008 were reviewed to identify factors associated with DCIS and DCIS with microinvasion (DCISM). Results: 88 patients (70.4%) had pure DCIS and 37 (29.6%) had DCISM. Among 33 DCIS patients who underwent SLNB, one patient (3.3%) was found to have isolated tumor cells in her biopsy, whereas 1 of 14 (37.8%) patients with DCISM had micrometastasis (7.1%). Similarly, of 16 patients (18.2%) with pure DCIS and axillary lymph node dissection (ALND) without SLNB, none had lymph node metastasis. Furthermore, of 20 patients with DCISM and ALND, only one (5%) had metastasis. In multivariate analysis, the presence of comedo necrosis [relative risk (RR)=4.1, 95% confidence interval (CI)=1.6-10.6, P=0.004], and hormone receptor (ER or PR) negativity (RR=4.0, 95%CI=1.5-11, P=0.007), were found to be significantly associated with microinvasion. Conclusions: Our findings suggest patients presenting with a preoperative diagnosis of DCIS associated with comedo necrosis or hormone receptor negativity are more likely to have a microinvasive component in definitive pathology following surgery, and should be considered for SLNB procedure along with patients who will undergo mastectomy due to DCIS.


        Comparison of In situ Dry Matter Degradation with In vitro Gas Production of Oak Leaves Supplemented with or without Polyethylene Glycol (PEG)

        Ozkan,,C.,Ozgur,Sahin,,M. Asian Australasian Association of Animal Productio 2006 Animal Bioscience Vol.19 No.8

        Dry matter (DM) degradation of leaves from Quercus cercis, Quercus libari, Quercus branti, and Quercus coccifera was determined using two different techniques: (i) in vitro gas production and (ii) the nylon bag degradability technique. In vitro gas production in the presence or absence of PEG and in situ DM disappearance were measured at 3, 6, 12, 24, 48, 72 and 96 h. In situ and in vitro DM degradation kinetics were described using the equation y = a+b ($1-e^{-ct}$). At all incubation times leaves from Quercus branti incubated with or without PEG gave significantly higher gas production than the other oak leaves except for 3 and 6 h incubation when leaves from Quercus branti without PEG supplementation only gave higher gas production than Quercus cercis and Quercus coccifera. At all incubation times except at 3, 6 and 12 h the DM disappearance from Quercus branti was significantly higher than the other species. Generally, PEG supplementation considerably increased the gas production at all incubation times and estimated parameters such as gas production rate ($c_{gas}$), gas production (ml) from the quickly soluble fraction ($a_{gas}$), gas production (b) from the insoluble fraction, potential gas production (a+b). However, all oak leaves did not give the same response to the PEG supplementation. Although the increase in gas production at 96 h incubation time was 8.9 ml for Quercus libari the increase was 5.5 ml for Quercus coccifera. It was concluded that except at early incubation times the relationships between the two methodologies seem to be sufficiently strong to predict degradability parameters from gas production parameters obtained in the presence or absence of PEG.

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        Oznur,Ozkan,K,l 호남수학회 2018 호남수학학술지 Vol.40 No.4

        In this paper, we investigate the majorization propertiesfor certain subclasses of analytic functions of complex order. Moreover, some interesting consequences of our main theorem arepointed out.

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