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Citation Count: 4
Accurate indoor positioning with ultra-wide band sensors
(Tubitak, 2020) Arsan, Taner
Ultra-wide band is one of the emerging indoor positioning technologies. In the application phase, accuracy and interference are important criteria of indoor positioning systems. Not only the method used in positioning, but also the algorithms used in improving the accuracy is a key factor. In this paper, we tried to eliminate the effects of off-set and noise in the data of the ultra-wide band sensor-based indoor positioning system. For this purpose, optimization algorithms and filters have been applied to the raw data, and the accuracy has been improved. A test bed with the dimensions of 7.35 m x 5.41 m and 50 cm x 50 cm grids has been selected, and a total of 27,000 measurements have been collected from 180 test points. The average positioning error of this test bed is calculated as 16.34 cm. Then, several combinations of algorithms are applied to raw data. The combination of Big Bang-Big Crunch algorithm for optimization, and then the Kalman Filter have yielded the most accurate results. Briefly, the average positioning error has been reduced from 16.34 cm to 7.43 cm.
Citation Count: 11
Accurate Refinement Of Docked Protein Complexes Using Evolutionary Information And Deep Learning
(Imperıal College Press, 2016) Delıbaş, Ayşe Bahar; Farhoodi, Roshanak; Pomplun, Marc; Haspel, Nurit
One of the major challenges for protein docking methods is to accurately discriminate native-like structures from false positives. Docking methods are often inaccurate and the results have to be refined and re-ranked to obtain native-like complexes and remove outliers. In a previous work we introduced AccuRefiner a machine learning based tool for refining protein-protein complexes. Given a docked complex the refinement tool produces a small set of refined versions of the input complex with lower root-mean-square-deviation (RMSD) of atomic positions with respect to the native structure. The method employs a unique ranking tool that accurately predicts the RMSD of docked complexes with respect to the native structure. In this work we use a deep learning network with a similar set of features and five layers. We show that a properly trained deep learning network can accurately predict the RMSD of a docked complex with 1.40 angstrom error margin on average by approximating the complex relationship between a wide set of scoring function terms and the RMSD of a docked structure. The network was trained on 35000 unbound docking complexes generated by RosettaDock. We tested our method on 25 different putative docked complexes produced also by RosettaDock for five proteins that were not included in the training data. The results demonstrate that the high accuracy of the ranking tool enables AccuRefiner to consistently choose the refinement candidates with lower RMSD values compared to the coarsely docked input structures.
Citation Count: 1
Analysis of the Patients and Physicians Connection Network on an online Health Information Platform
(IOS Press, 2014) Aydın, Mehmet Nafiz; Perdahci, N. Ziya
Social network applications have gained popularity in the health domain as they bring health information seekers (patients and alike) and medication advice providers (physicians and other relevant actors) together. By employing a network science perspective this research is aimed to understand an information network establishing connections among and between information seekers and providers. We found that such a connection network surfaces most of the essential characteristics of a typical complex network. Furthermore a detailed structural analysis shows some intriguing relations and connection behaviours in the network. Implications of the findings are discussed from the perspectives of medical informatics and social network analysis.
Citation Count: 4
Atomic force microscopy and spectroscopy studies of annealed Ce/Ti/Zr mixed oxide thin films prepared by sol-gel process
(Elsevier Science Bv, 2006) Ghodsi, Farhad E.; Tepehan, Fatma Zehra; Tepehan, Galip Gültekin
Mixed Ce/Ti/Zr oxide thin films with a molar ratio of 0.5:0.25:0.25 were prepared using the sol-gel process and deposited on glass substrates by the dip coating technique. The effect of heat treatment temperature on surface morphology of the films was examined by atomic force microscopy AFM. The optical transmittance and reflectance of the films were measured over the spectral range from 350 to 1000 nm. The refractive index and extinction coefficient and thickness of the films were determined as a function of the heat treatment temperature. The refractive index increased from 1.51 to 2.02 at lambda = 600 nm and the extinction coefficient values increased from 0.006 to 0.094 while the thickness of the films decreased from 81 nm to 45 nm when annealing temperature increased from 100 degrees C to 500 degrees C. The results show that the optical properties and surface morphology of the mixed Cc/Ti/Zr oxide thin films were affected by annealing temperature. (c) 2006 Elsevier B.V. All rights reserved.
Citation Count: 13
Bayesian Compressive Sensing For Primary User Detection
(Inst Engineering Technology-IET, 2016) Erküçük, Serhat; Erküçük, Serhat; Cirpan, Hakan Ali
In compressive sensing (CS)-based spectrum sensing literature most studies consider accurate reconstruction of the primary user signal rather than detection of the signal. Furthermore possible absence of the signal is not taken into account while evaluating the spectrum sensing performance. In this study Bayesian CS is studied in detail for primary user detection. In addition to assessing the signal reconstruction performance and comparing it with the conventional basis pursuit approach and the corresponding lower bounds signal detection performance is also considered both analytically and through simulation studies. In the absence of a primary user signal the trade-off between probabilities of detection and false alarm is studied as it is equally important to determine the performance of a CS approach when there is no active primary user. To reduce the computation time and yet achieve a similar detection performance finally the effect of number of iterations is studied for various systems parameters including signal-to-noise-ratio compression ratio mean value of accumulated energy and threshold values. The presented framework in this study is important in the overall implementation of CS-based approaches for primary user detection in practical realisations such as LTE downlink OFDMA as it considers both signal reconstruction and detection.
Citation Count: 1
Bayesian estimation of discrete-time cellular neural network coefficients
(TUBITAK Scientific & Technical Research Council Turkey, 2017) Şenol, Habib; Özmen, Atilla; Şenol, Habib
A new method for finding the network coefficients of a discrete-time cellular neural network (DTCNN) is proposed. This new method uses a probabilistic approach that itself uses Bayesian learning to estimate the network coefficients. A posterior probability density function (PDF) is composed using the likelihood and prior PDFs derived from the system model and prior information respectively. This posterior PDF is used to draw samples with the help of the Metropolis algorithm a special case of the Metropolis--Hastings algorithm where the proposal distribution function is symmetric and resulting samples are then averaged to find the minimum mean square error (MMSE) estimate of the network coefficients. A couple of image processing applications are performed using these estimated parameters and the results are compared with those of some well-known methods.
Citation Count: 3
Beliefs of Living Donors About Recipients' End-Stage Liver Failure and Surgery for Organ Donation
(Elsevier Science Inc, 2017) Krespi, Margörit Rita; Tankurt, A.; Acarli, Koray; Kanmaz, Turan; Yankol, Yucel; Kalayoğlu, Murat
Background. The concept of beliefs could provide a basis for how donors may perceive recipients' end-stage liver failure (ESLF) and surgery for organ donation. However there is no such quantitative study. Therefore the objective of this study was to explore beliefs of living donors about recipients' ESLF and surgery for organ donation. Methods. The sample comprised 16 living donors who donated a part of their liver to a patient who had ESLF. The data were analyzed by following established procedures for inductive qualitative analysis. Results. Analysis showed that donors' beliefs can be viewed in a number of groups. Beliefs about recipients' ESLF included diverse explanations for ESLF (blaming oneself and physicians) and physical symptoms (developmental slowing down). Beliefs about being a donor included reasons for being a donor (performing a good deed being healed) barriers to being a donor (other people being ignorant and selfish) ways to manage these barriers (following one's gut feeling) and factors facilitating being a donor (the feeling that one does not have many people to leave behind). Beliefs about surgery for organ donation included physical effects (pain feeling stiff). Beliefs about organ donation included views that general organ donation should be encouraged and that people's awareness should be raised. Conclusions. Existing psychological perspectives could help to interpret some beliefs. Nevertheless other beliefs not previously reported could be considered as targets for individual consultations/psycho-educational programs for fostering emotional well-being.
Citation Count: 1
Broadband matching via reflection function optimization
(Wiley, 2017) Şengül, Metin
In this paper a practical approach is presented for designing broadband matching networks via reflection function optimization. In the proposed algorithm the input or output reflection function of the matching network is expressed in terms of three real polynomials describing the matching network load and generator reflection coefficients. Next one of the polynomials is optimized to get minimum reflection function values in the passband. Then matching network topology and element values are obtained via the formed input reflection coefficient expression. Two examples are presented to explain the usage of the new approach. Copyright (c) 2016 John Wiley & Sons Ltd.
Citation Count: 2
Broadband Matching via Unequal Length Cascaded Transmission Lines
(World Scientific Publ Co Pte Ltd, 2017) Şengül, Metin
In this paper a new approach based on the real frequency technique (RFT) has been proposed to solve broadband matching problems using cascaded unequal length transmission lines. At the end of the design process optimum characteristic impedance and delay values of transmission lines are obtained. Two examples are given to illustrate the utilization of the proposed approach.
Citation Count: 0
Broadband Microwave Amplifier Design with Lumped Elements
(Walter De Gruyter Gmbh, 2016) Şengül, Metin
This study introduces a broadband microwave amplifier design that utilizes the measured scattering parameters of active devices without assuming an initial topology for the matching networks or an analytic form of the system transfer function. The algorithm can be extended to design multistage broadband microwave amplifiers. An example is given to illustrate the application of the proposed method. It was found that the proposed method provides very good initials for CAD tools to further improve amplifier performance by working on the element values.
Citation Count: 16
Cation Effect on Slow Release from Alginate Beads: A Fluorescence Study
(Springer/Plenum Publishers, 2014) Pekcan, Mehmet Önder; Erim, F. Bedia; Pekcan, Önder; Evingür, Gülşen Akin
In this study spherical alginate beads containing pyranine (P-y) as a fluorescence probe were prepared by ionotropic gelation of a sodium alginate solution. The steady state fluorescence technique was used to study pyranine release from the alginate beads crosslinked with calcium barium and aluminum ions respectively. The slow release of P-y was observed with the time drive mode of the spectrophotometer at 512 nm. Fluorescence emission intensity (I-p) from P-y was monitored during the release process and the encapsulation efficiency (EE) of pyranine from the alginate beads was calculated. The Fickian Diffusion model was used to measure the release coefficients D-sl. It was seen that the slow release coefficients of pyranine from the alginate beads crosslinked with Ca2+ Ba2+ and Al3+ ions increased in the following order: D-sl (Al3+)> D-sl (Ca2+)> D-sl (Ba2+). In contrast the initial amount of pyranine and EE into the beads showed the reverse behavior.
Citation Count: 13
Characterization Of Mps Capped Cds Quantum Dots And Formation Self-Assembled Quantum Dots Thin Films On A Glass Substrate
(Natl Inst R&D Materials Physics, 2011) Koç, Kenan; Tepehan, Fatma Zehra; Tepehan, Galip Gültekin
Colloidal powdered and thin film forms of MPS capped CdS quantum dots have been produced by combination of colloidal chemistry and sol-gel method. Nanoparticles were self-assembled directly on a glass substrate using spin coating method without introducing any matrix. Colloidal powdered and thin film forms were characterised by absorbance photolimunescence XRD FT-IR HRTEM and AFM measurements. The HRTEM images give a grain size of 2.5-3.0 nm and this is in agreement with the values found in the absorbance and XRD measurement. Average size of the quantum dots increase with increasing of heat treatment temperature due to Oswald ripening.
Citation Count: 0
A characterization of totally umbilical hypersurfaces of a space form by geodesic mapping
(Springer, 2013) Canfes, Elif Ozkara; Özdeğer, Abdülkadir
The idea of considering the second fundamental form of a hypersurface as the first fundamental form of another hypersurface has found very useful applications in Riemannian and semi-Riemannian geometry especially when trying to characterize extrinsic hyperspheres and ovaloids. Recently T. Adachi and S. Maeda gave a characterization of totally umbilical hypersurfaces in a space form by circles. In our paper we give a characterization of totally umbilical hypersurfaces of a space form by means of geodesic mapping.
Citation Count: 0
Chebyshev nets formed by Ricci curves in a 3-dimensional Weyl space
(Elsevier Science Bv, 2005) Yıldırım, Gülçin Çivi; Özdeğer, Abdülkadir
In this paper Ricci curves in a 3-dimensional Weyl space W-3(g T) are defined and it is shown that any 3-dimensional Chebyshev net formed by the three families of Ricci curves in a W-3(g T) having a definite metric and Ricci tensors is either a geodesic net or it consists of a geodesic subnet the members of which have vanishing second curvatures. In the case of in indefinite Ricci tensor only one of the members of the geodesic subnet under consideration has a vanishing second curvature. (c) 2004 Elsevier B.V. All rights reserved.
Citation Count: 21
Conductivity percolation of carbon nanotubes (CNT) in polystyrene (PS) latex film
(Canadian Science Publishing Nrc Research Press, 2010) Pekcan, Mehmet Önder; Yargı, Önder; Pekcan, Önder
In this study the effect of multiwalled carbon nanotubes (MWNT) on film formation behaviour and electrical conductivity properties of polystrene (PS) latex film was investigated by using the photon transmission technique and electrical conductivity measurements. Films were prepared by mixing PS latex with different amounts of MWNTs varying in the range between 0 and 20 wt%. After drying MWNT content films were separately annealed above the glass transition temperature (T-g) of PS ranging from 100 to 270 degrees C for 10 min. To monitor film formation behavior of PS-MWNT composites transmitted light intensity I-tr was measured after each annealing step. The surface conductivity of annealed films at 170 degrees C was measured and found to increase dramatically above a certain fraction of MWNT (4 wt%) following the percolation theory. This fraction was defined as the percolation threshold of conductivity R-c. The conductivity scales with the mass fraction of MWNT as a power law with exponent 2.27 which is extremely close to the value of 2.0 predicted by percolation theory. In addition the increase in I-tr during annealing was explained by void closure and interdiffusion processes. Film formation stages were modeled and the corresponding activation energies were measured.
Citation Count: 1
Continuous dependence on data for a solution of the quasilinear parabolic equation with a periodic boundary condition
(Springer International Publishing Ag, 2013) Kanca, Fatma; Baglan, Irem Sakinc; Kanca, Fatma
In this paper we consider a parabolic equation with a periodic boundary condition and we prove the stability of a solution on the data. We give a numerical example for the stability of the solution on the data.
Citation Count: 6
Corporate Governance and Tunneling: Empirical Evidence from Turkey
(Economics Bulletin, 2018) Selçuk, Elif Akben; Şener Tournus, Pınar
This study investigates whether internal governance mechanisms affect tunneling through intercorporate loans for a sample of Turkish listed non-financial firms over the period 2006 to 2014. While the findings reveal a significant and positive relationship between state ownership and tunneling and a significant and negative relationship between foreign ownership and tunneling the relationship between family ownership and tunneling is non-linear. In addition while board size is negatively associated with tunneling independent directors do not prevent the embezzlement of resources. Furthermore the results indicate that while older firms firms with family chairman and higher growth opportunities are more likely to engage in tunneling activities firm size high cash holding leverage and financial distress do not affect tunneling.
Citation Count: 2
Corrected Panel-Reactive Antibody Positivity Rates for Hypersensitized Patients in Turkish Population With Calculated Panel-Reactive Antibody Software
(Elsevier Science Inc, 2017) Yelekçi, Kemal; Akgül, Sebahat Usta; Öğret, Yeliz; Çiftçi, Hayriye Şentürk; Bayraktar, Adem; Bakkaloğlu, Hüseyin; Çalışkan, Yaşar Kerem; Yelekçi, Kemal; Türkmen, Aydin; Aydın, Ali Emin; Oğuz, Fatma Savran; Çarin, Mahmut Nezih; Aydın, Filiz
however the rate was 86.2% using the cPRA. Discussion. cPRA shows the rate of the rejected donors according to all unacceptable antigens. The need for a list of unacceptable antigens in place of the PRA positivity rate is a real change in the sensitization-dependent calculation as cPRA positivity rate. Conclusion. In principal implementation of cPRA will encourage many centers and laboratories to adopt a standard measurement of sensitization in Turkey. It will increase the chances of better donor match particularly for hypersensitized patients by the creation of an unacceptable mismatch program using cPRA software.
Citation Count: 19
Critical Exponents of Kappa Carrageenan in the Coil-Helix and Helix-Coil Hysteresis Loops
(Taylor & Francis Inc, 2009) Pekcan, Mehmet Önder; Kara, Selim; Pekcan, Önder
The steady-state fluorescence technique was used to study coil-helix (sol-gel) and helix-coil (gel-sol) transitions of the kappa carrageenan-water system with various carrageenan contents. Fluorescence (I) and scattered light (I-sc) intensities were measured against temperature to determine critical phase transition temperatures and exponents. It was observed that the coil-helix transition temperatures T-ch were much lower than the helix-coil (T-hc) transition temperatures due to the hysteresis of the phase transition loops. The gel fraction exponent (beta) was measured and found to be in accord with the classical Flory-Stockmayer model.
Citation Count: 15
Critical Exponents of Photoinitiated Gelation at Different Light Intensities
(Taylor & Francis Inc, 2009) Pekcan, Mehmet Önder; Arsu, Nergis; Pekcan, Önder
A photo-differential scanning calorimetric (Photo-DSC) technique was used to study the photoinitiated radical polymerization of a 75% epoxy diacrylate (EA) and 25% tripropyleneglycoldiacrylate (TPGDA) mixture with 2-mercaptothioxanthone (TX-SH) as photoinitiator by using different light intensities. Photopolymerization reactions were carried out under identical conditions of temperature and initiator concentration. It was observed that all conversion curves during gelation at various Might intensities present good sigmoidal behavior as predicted by the percolation model. Observations around the critical time called the glass transition point (t(g)) taken for polymerization to reach the maximum rate (R-pmax) show that the gel fraction exponents beta obeyed the universal percolation picture. On the other hand R-pmax t(g) and final conversion values were found to be dependent on the UV light intensity.

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