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Öğe Optical parameters of calix[4]arene films and their response to volatile organic vapors(ELSEVIER SCIENCE SA, 2011) Özbek, Z.; Capan, R.; Göktas, H.; Şen, S.; İnce, F. G.; Özel, Mehmet Emin; Davis, F.The Langmuir-Blodgett (LB) technique was employed to produce thin LB films using an amphiphilic calix-4-resorcinarene onto different substrates such as quartz, gold coated glass and quartz crystals. The characteristics of the calix LB films are assessed by UV-visible, quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) measurements. UV-vis and QCM measurements indicated that this material deposited very well onto the solid substrates with a transfer ratio of >0.95. Using SPR data, the thickness and refractive index of this LB film are determined to be 1.14 nm/deposited layer and 1.6 respectively. The sensing application of calixarene LB films towards volatile organic vapors such as chloroform, benzene, toluene and ethanol vapors is studied by the SPR technique. The response of this LB film to saturated chloroform vapor is much larger than for the other vapors. The response is fast and fully recoverable. It can be proposed that this sensing material deposited onto gold coated glass substrates has a good sensitivity and selectivity for chloroform vapor. This material may also find potential applications in the development of room temperature organic vapor sensing devices.Öğe Performance comparison of different regression methods for vo(2)max estimation(IEEE, 2013) Akturk, Erman; Akay, M. Fatih; Kilitcioglu, HasanThe purpose of this paper is to develop maximal oxygen uptake (VO(2)max) models by using different regression methods such as Multilayer Feed-Forward Artificial Neural Networks (MFANN's), Support Vector Regression (SVR), Generalized Regression Neural Networks (GRNN's) and Multiple Linear Regression (MLR). The dataset includes data of 439 subjects and the input variables of the dataset are gender, age, body mass index (BMI), percent body fat (BF), respiratory exchange ratio (RER) from treadmill test, self-reported rating of perceived exertion (RPE) from treadmill test, heart rate (HR) and time to exhaustion from treadmill test. The performance of the models is evaluated by calculating their standard error of estimates (SEE) and multiple correlation coefficients (R). The results suggest that MFANN-based VO(2)max prediction models perform better than other prediction models.Öğe Xmm-newton observatıons of lumınous sources ın nearby galaxıes ngc 4395, ngc 4736, and ngc 4258(IOP PUBLISHING LTD, 2013) Akyuz, A.; Kayaci, S.; Avdan, H.; Özel, Mehmet Özel; Sonbas, E.; Balman, S.We present the results of a study of non-nuclear discrete sources in a sample of three nearby spiral galaxies (NGC 4395, NGC 4736, and NGC 4258) based on XMM-Newton archival data supplemented with Chandra data for spectral and timing analyses. A total of 75 X-ray sources have been detected within the D-25 regions of the target galaxies. The large collecting area of XMM-Newton makes the statistics sufficient to obtain spectral fitting for 16 (about 20%) of these sources. Compiling the extensive archival exposures available, we were able to obtain the detailed spectral shapes of diverse classes of point sources. We have also studied temporal properties of these luminous sources. Eleven of them are found to show short-term (less than 80 ks) variation while eight of them show long-term variation within factors of similar to 2-5 during a time interval of similar to 2-12 years. Timing analysis provides strong evidence that most of these sources are accreting X-ray binary systems. One source that has properties different from others was suspected to be a supernova remnant, and our follow-up optical observation confirmed this. Our results indicate that sources within the three nearby galaxies are showing a variety of source populations, including several ultraluminous X-ray sources, X-ray binaries, transients together with a super soft source, and a background active galactic nucleus candidate.Öğe p-phthalimidobenzoic thin film for volatile organic vapor detection(2010) Şen, Sibel; Çapan, Rifat; Özel, Mehmet Emin; Hassan A.K.; Namli H.; Turhan O.Thin films of the molecule of p-phthalimidobenzoic acid (FIBA) have been deposited by spin coating and are studied for application as sensing membrane for the detection of alcohols. Atomic force microscopy (AFM) and surface plasmon resosnance (SPR) were used for the characterisation of the FIBA films. Alcohol sensing properties of the obtained films were examined using SPR measurements. AFM images show that FIBA films have the large surface roughness with an estimated roughness RMS value of 6.3 nm. Films with such compact and granular morphology are believed to provide improved sensitivity when used in sensor applications. The measured SPR curves were analysed by applying a least square fitting procedure using Fresnel's reflection theory. FIBA film used as a sensing element for the detection of saturated 2-propanol, ethanol and methanol vapors. Fast response and recovery for all studied analytes have been obtained. These results show that thin films made with this FIBA molecule are demonstrating good suitability for room temperature vapor application.Öğe Performance comparison of different regression methods for VO2max ESTIMATION [VO2max tahmini için farkli regresyon yöntemlerinin performans Karsilastirmas](2013) Aktürk, Erman; Akay, Mehmet Fatih; Kilitçioğlu, HasanThe purpose of this paper is to develop maximal oxygen uptake (VO 2max) models by using different regression methods such as Multilayer Feed-Forward Artificial Neural Networks (MFANN's), Support Vector Regression (SVR), Generalized Regression Neural Networks (GRNN's) and Multiple Linear Regression (MLR). The dataset includes data of 439 subjects and the input variables of the dataset are gender, age, body mass index (BMI), percent body fat (BF), respiratory exchange ratio (RER) from treadmill test, self-reported rating of perceived exertion (RPE) from treadmill test, heart rate (HR) and time to exhaustion from treadmill test. The performance of the models is evaluated by calculating their standard error of estimates (SEE) and multiple correlation coefficients (R). The results suggest that MFANN-based VO2max prediction models perform better than other prediction models.Öğe Grb 081008: from burst to afterglow and the transıtıon phase ın between(IOP PUBLISHING LTD, 2010) Yuan, F.; Schady, P.; Racusin, J. L.; Willingale, R.; Kruehler, T.; O'Brien, P. T.; Greiner, J.; Oates, S. R.; Rykoff, E. S.; Aharonian, F.; Akerlof, C. W.; Ashley, M. C. B.; Barthelmy, S. D.; Filgas, R.; Flewelling, H. A.; Gehrels, N.; Goegues, E.; Guever, T.; Horns, D.; Kiziloglu, Ue.; Krimm, H. A.; McKay, T. A.; Özel, Mehmet Emin; Phillips, A.; Quimby, R. M.; Rowell, G.; Rujopakarn, W.; Schaefer, B. E.; Vestrand, W. T.; Wheeler, J. C.; Wren, J.We present a multi-wavelength study of GRB 081008, at redshift 1.967, by Swift, ROTSE-III, and Gamma-Ray Burst Optical/NearInfrared Detector. Compared to other Swift GRBs, GRB 081008 has a typical gamma-ray isotropic equivalent energy output (similar to 10(53) erg) during the prompt phase, and displayed two temporally separated clusters of pulses. The early X-ray emission seen by the Swift X-Ray Telescope was dominated by the softening tail of the prompt emission, producing multiple flares during and after the Swift Burst Alert Telescope detections. Optical observations that started shortly after the first active phase of gamma-ray emission showed two consecutive peaks. We interpret the first optical peak as the onset of the afterglow associated with the early burst activities. A second optical peak, coincident with the later gamma-ray pulses, imposes a small modification to the otherwise smooth light curve and thus suggests a minimal contribution from a probable internal component. We suggest the early optical variability may be from continuous energy injection into the forward shock front by later shells producing the second epoch of burst activities. These early observations thus provide a potential probe for the transition from the prompt phase to the afterglow phase. The later light curve of GRB 081008 displays a smooth steepening in all optical bands and X-ray. The temporal break is consistent with being achromatic at the observed wavelengths. Our broad energy coverage shortly after the break constrains a spectral break within optical. However, the evolution of the break frequency is not observed. We discuss the plausible interpretations of this behavior.Öğe A new difference-based weighted mixed Liu estimator in partially linear models(TAYLOR & FRANCIS LTD, 2018) Akdeniz, Esra; Akdeniz, Fikri; Roozbeh, MahdiIn this paper, a generalized difference-based estimator is introduced for the vector parameter beta in the partially linear model when the errors are correlated. A generalized difference-based Liu estimator is defined for the vector parameter beta. Under the linear stochastic constraint r = R beta + e, a new generalized difference-based weighted mixed Liu estimator is introduced. The performance of this estimator over the generalized difference-based weighted mixed estimator and the generalized difference-based Liu estimator in terms of the mean squared error matrix criterion is investigated. Then, a method to select the biasing parameter d and non-stochastic weight. is considered. The efficiency properties of the newestimator are illustrated by a simulation study. Finally, the performance of the new estimator is evaluated for a real data set.Öğe Neural network based VO2max prediction models using maximal exercise and non-exercise data [Maksimal egzersiz ve egzersize dayali olmayan verileri kullanarak sinir agi tabanli VO2MAX tahmin modelleri](2013) Aktarla ,Ece; Akay, Mehmet Fatih; Aktürk, Erman; Açikkar, MustafaArtificial Neural Network (ANN) models based on maximal and non-exercise (N-Ex) variables are developed to predict maximal oxygen uptake (VO 2max) the input variables of the dataset are gender, age, body mass index (BMI), grade, selfreported rating of perceived exertion (RPE) from treadmill test, heart rate (HR), perceived functional ability (PFA) and physical activity rating (PA-R). The performance of the models is evaluated by calculating their standard error of estimate (SEE) and multiple correlation coefficient (R). The results suggest that the performance of VO2max prediction models based on maximal and standard N-Ex variables (i.e. gender, age, BMI etc) can be improved by including questionnaire variables (PFA and PA-R) in the models.Öğe Generalized difference-based weighted mixed almost unbiased ridge estimator in partially linear models(Springer New York LLC, 2017) Akdeniz, Fikri; Roozbeh, MehdiIn this paper, a generalized difference-based estimator is introduced for the vector parameter (Formula presented.) in partially linear model when the errors are correlated. A generalized difference-based almost unbiased ridge estimator is defined for the vector parameter (Formula presented.). Under the linear stochastic constraint (Formula presented.), a new generalized difference-based weighted mixed almost unbiased ridge estimator is proposed. The performance of this estimator over the generalized difference-based weighted mixed estimator, the generalized difference-based estimator, and the generalized difference-based almost unbiased ridge estimator in terms of the mean square error matrix criterion is investigated. Then, a method to select the biasing parameter k and non-stochastic weight (Formula presented.) is considered. The efficiency properties of the new estimator is illustrated by a simulation study. Finally, the performance of the new estimator is evaluated for a real dataset.Öğe Lookıng into the fireball: rotse-ııı and swıft observatıons of early gamma-ray burst afterglows(IOP PUBLISHING LTD, 2009) Rykoff, E. S.; Aharonian, F.; Akerlof, C. W.; Ashley, M. C. B.; Barthelmy, S. D.; Flewelling, H. A.; Gehrels, N.; Gogus, E.; Guver, T.; Kiziloglu, Ue.; Krimm, H. A.; McKay, T. A.; Özel, Mehmet; Phillips, A.; Quimby, R. M.; Rowell, G.; Rujopakarn, W.; Schaefer, B. E.; Smith, D. A.; Vestrand, W. T.; Wheeler, J. C.; Wren, J.; Yuan, F.; Yost, S. A.We report on a complete set of early optical afterglows of gamma-ray bursts (GRBs) obtained with the Robotic Optical Transient Search Experiment (ROTSE-III) telescope network from 2005 March through 2007 June. This set is comprised of 12 afterglows with early optical and Swift/X-Ray Telescope observations, with a median ROTSE-III response time of 45 s after the start of gamma-ray emission (8 s after the GCN notice time). These afterglows span 4 orders of magnitude in optical luminosity, and the contemporaneous X-ray detections allow multi-wavelength spectral analysis. Excluding X-ray flares, the broadband synchrotron spectra show that the optical and X-ray emission originate in a common region, consistent with predictions of the external forward shock in the fireball model. However, the fireball model is inadequate to predict the temporal decay indices of the early afterglows, even after accounting for possible long-duration continuous energy injection. We find that the optical afterglow is a clean tracer of the forward shock, and we use the peak time of the forward shock to estimate the initial bulk Lorentz factor of the GRB outflow, and find 100 less than or similar to Gamma(0) less than or similar to 1000, consistent with expectations.Öğe Near-resonant diurnal reactions: A physical model applicable to origin of life processes(2012) Budding, Edwin; Akı, Cüneyt; Demircan, Osman; Gündüz, Bülent; Gündüz, Güngör; Emin özel, MehmetWe adopt that the large residual chemical potential energy (CPE) among reagents of the biosphere constitutes the key physical problem posed by life. We associate the formation of this CPE with the nearresonant behaviour of a two-stage 'A-B' molecular process that behaves as a self-sustaining parametric oscillator. Under suitable conditions, such an oscillator generates CPE when forced by a periodic (daily) insolation. The net growth factor required to explain the current mean excess of biospheric CPE is ?5×10 -12 d -1 . This aligns with the mean exponential coefficient of secular oxygen generation in the terrestrial atmosphere. It is also consistent with a feasible scale of oxygen production in certain prebiotic natural photosynthesis scenarios, that can be candidates for the initial A subprocess on the Earth. We schematize initial evolutionary development of the A-B process, including the important role of the intermediate AB compound that provides negative feedback. Supportive C-type molecules also develop as a by-product. The diurnally related distribution of H 2 O 2 on Mars may illustrate a comparable proto-biospheric scheme, and there may be analogous processes on Jupiter. The exponential growth in the lengths of terrestrial nucleotide chain molecules also supports its validity, as does the corresponding growth in measures of cellular complexity. We compare the scenario's implications with biological evidence on the possible co-evolution of blue-light photoreception and circadian timing in Archean photoautotrophs. We consider how a surviving level of cellular organization of circadian rhythmicity, from ancient through to modern times, may be interpreted along these lines, comparing our model with a previously published, comparable, biochemical one.Öğe Restricted estimator in two seemingly unrelated regression model(unıv punjab, 2016) Erdugan, Funda; Akdeniz, FikriThis article is concerned with the estimation problem of multicollinearity in two seemingly unrelated regression (SUR) equations with linear restrictions. We propose a restricted feasible SUR estimates of the regression coefficients of this model and compare with feasible generalized least squares (FGLS) estimator and the estimator proposed by Revankar (1974) in the matrix mean square error sense. The ideas in the article are evaluated using Monte Carlo simulation.Öğe The distribution of the Liu-type estimator of the biasing parameter in elliptically contoured models(Taylor & Francıs ınc, 2017) Arashi, M.; Nadarajah, Saralees; Akdeniz, FikriWe derive the density function of the stochastic shrinkage parameters of the Liu-type estimator in elliptical models. The correctness of derivation is checked by simulations. A real data application is also provided.Öğe Neural Network Based VO(2)max Prediction Models Using Maximal Exercise and Non-Exercise Data(IEEE, 2013) Aktarla, Ece; Akay, M. F.; Akturk, Erman; Acikkar, MustafaArtificial Neural Network (ANN) models based on maximal and non-exercise (N-Ex) variables are developed to predict maximal oxygen uptake (VO(2)max) the input variables of the dataset are gender, age, body mass index (BMI), grade, self-reported rating of perceived exertion (RPE) from treadmill test, heart rate (HR), perceived functional ability (PFA) and physical activity rating (PA-R). The performance of the models is evaluated by calculating their standard error of estimate (SEE) and multiple correlation coefficient (R). The results suggest that the performance of VO(2)max prediction models based on maximal and standard N-Ex variables (i.e. gender, age, BMI etc) can be improved by including questionnaire variables (PFA and PA-R) in the models.Öğe Thin film characterization of novel phthalimide materials(NATL INST OPTOELECTRONICS, 2011) Şen, Sibel; Capan, Rifat; Ozel, Mehmet Emin; Hassan, A. K.; Turhan, O.; Namli, H.Spin coating technique is employed to produce thin phthalimide films using novel p-phthalimidobenzoic acid (FIBA) and N-(phthalimido)-p-aminobenzoic acid (FIABA) materials. Several spin speeds and various solution concentrations are chosen to monitor the thin film deposition process of these new materials. The optical properties are studied using UV-visible spectroscopy and spectroscopic ellipsometry methods. The absorption of the FIBA and FIABA films against the spin speed showed an exponential behavior. pi -> pi* transition is occurred. The thicknesses of thin films at 2000 rpm are obtained 15.86 nm for FIBA and 12.99 nm for FIABA using spectroscopic ellipsometry results.Öğe On the classical Maki-Thompson rumour model in continuous time(SPRINGER, 2011) Belen, Selma; Kropat, Erik; Weber, Gerhard-WilhelmIn this paper, the Maki-Thompson model is slightly refined in continuous time, and a new general solution is obtained for each dynamics of spreading of a rumour. It is derived an equation for the size of a stochastic rumour process in terms of transitions. We give new lower and upper bounds for the proportion of total ignorants who never learned a rumour and the proportion of total stiflers who either forget the rumour or cease to spread the rumour when the rumour process stops, under general initial conditions. Simulation results are presented for the analytical solutions. The model and these numerical results are capable to explain the behaviour of the dynamics of any other dynamical system having interactions similar to the ones in the stochastic rumour process and requiring numerical interpretations to understand the real phenomena better. The numerical process in the differential equations of the model is investigated by using error-estimates. The estimated error is calculated by the Runge-Kutta method and found either negligible or zero for a relatively small size of the population. This pioneering paper introduces a new mathematical method into Operations research, motivated by various areas of scientific, social and daily life, it presents numerical computations, discusses structural frontiers and invites the interested readers to future research.Öğe A search for supernova remnants in the nearby spiral galaxy M 74 (NGC 628)(2010) Sonbaş, E.; Akyüz, A.; Balman, Ş.; Özel, Mehmet EminAn optical search was carried out for supernova remnants (SNRs) in the Sc type nearby spiral galaxy M74, using ground-based observations at the TUBITAK National Observatory (TUG, Antalya/Turkey) and the Special Astrophysics Observatory (SAO, Russia). Observations were supplemented by the spectral analysis of archived X-ray data from XMM-Newton and Chandra. The survey of M74 covered ?9 arcmin2 with [S II], H?, and their continuum filters. Interference filter images of M74 were obtained the with the 1.5 m Russian Turkish Telescope (RTT150) at TUG and spectral data taken with the 6 m Bolsoi Azimuthal Telescope (BTA) at SAO. The emission nebulae with continuum-subtracted line ratio values of [S II]??6716,6731 /H? ? 0.4 are identified as SNRs. Followup spectroscopy confirmed optical SNR identifications. We have identified nine new SNR candidates in M74 with [S II]/H? ? 0.4 as the basic criterion. The [S II]/H? ratio ranges from 0.40 to 0.91 and H? intensities from 2.8 × 10 -15 erg cm-2 s-1 to 1.7 × 10 -14 erg cm-2 s-1. We also present spectral follow-up observations of these SNR candidates, however, we are able to spectrally confirm only three of them (SNR2, SNR3, and SNR5). The lack of confirmation for the rest might come from contamination by the nearby H II emission regions, as well as from the inaccurate positioning of the long slit on these objects. In addition, we searched the XMM-Newton and Chandra Observatory archival data for the X-ray counterparts to the optically identified candidates. We find positional coincidence with only three SNR candidates, SNR1, SNR2, and SNR8. The spectrum of SNR2 yields a shock temperature of 10.8 keV with an ionization timescale of 1.6 × 10-10 s cm-3, indicating a relatively young remnant in an early Sedov phase, which is not supported by our optical wavelength analysis. Given the high luminosity of 10-39 erg s-1 and the characteristics of the X-ray spectrum, we favor an ultra luminous X-ray source interpretation for this source associated with an SNR.We calculated an X-ray flux upper limit of 9.0 × 10-15 erg cm-2 s-1 for the rest of the SNRs, including spectroscopically identified SNR3 and SNR5.Öğe Efficiency of the generalized-difference-based weighted mixed almost unbiased two-parameter estimator in partially linear model(TAYLOR & FRANCIS INC, 2017) Akdeniz, Fikri; Roozbeh, MahdiIn this paper, a generalized difference-based estimator is introduced for the vector parameter in partially linear model when the errors are correlated. A generalized-difference-based almost unbiased two-parameter estimator is defined for the vector parameter . Under the linear stochastic constraint r = R + e, we introduce a new generalized-difference-based weighted mixed almost unbiased two-parameter estimator. The performance of this new estimator over the generalized-difference-based estimator and generalized- difference-based almost unbiased two-parameter estimator in terms of the MSEM criterion is investigated. The efficiency properties of the new estimator is illustrated by a simulation study. Finally, the performance of the new estimator is evaluated for a real dataset.Öğe Asymptotic behavior of the zero solutions to generalized pipe and rotating shaft equations(2000) Kurt, AyferA non-autonomous partial differential equation describing the dynamics of a uniform pipe and a system describing the dynamics of a rotating shaft are considered. Sufficient conditions for the global asymptotic stability of the zero solution of the boundary value problem for the differential equation and the system under consideration are established by using the Lyapunov function technique.Öğe Revıvıng some geometrıc aspects of shrınkage estımatıon ın lınear models(ANKARA UNIV, FAC SCI, 2019) Akdeniz, Fikri; Özturk, FikriIt is well known that the least squares estimator is the best linear unbiased estimator of the parameter vector in a classical linear model. But, it is 'too long' as a vector and unreliable, confidence intervals are broad for some components especially in the case of multicollinearity. Shrinkage (contraction) type estimators are efficient remedial tools in order to solve problems caused by multicollinearity. In this study, we consider a class of componentwise shrunken estimators with typical members: Mayer and Willke's contraction estimator, Marquardt's principal component estimator, Hoerl and Kennard's ridge estimator, Liu's linear unified estimator and a discrete shrunken estimator. All estimators considered are "shorter" than the least squares estimator with respect to the Euclidean norm, biased, but insensitive to multicollinearity and admissible within the set of linear estimators with respect to unweighted squared error risk. Some behaviors of these estimators are illustrated geometrically by tracing their trajectories as functions of shrinkage factors in a two-dimensional parameter space.
