Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 9Citation - Scopus: 9Synthesis and Characterization of Novel High Temperature Structural Adhesives Based on Nadic End Capped Mda-Btda Copolyimide(IOP Publishing Ltd., 2018) Acar, Oktay; Varış, Serhat; Işık, Tuğba; Tirkeş, Seha; Demir, Mustafa MuammerA series of novel copolyimide structural adhesives were synthesized using 4,4′-diaminodiphenylmethane (MDA), 3,4′-oxydianiline (ODA) and 3,3′,4,4′-benzophenonetetracarboxylic acid dianhydride (BTDA) as co-monomers, and nadic anhydride as an end cap reagent. The adhesives with different MDA and ODA contents were examined in terms of their structure, thermal stability, mechanical properties, and adhesive performance. They have glass transition temperatures (T g) about 400 °C, with thermal stability up to 500 °C. The effect of diamine monomer compositions on adhesion performance and processability of the copolyimides were studied. The copolyimides exhibited adhesion strength up to 16.3 MPa at room temperature. Nadic end capped MDA-BTDA-ODA copolyimide resins gained adjustable and controllable processability with the addition of ether bridged aromatic segments. The copolyimide adhesive with equimolar composition of MDA:ODA is distinguished form the both commercial PMR-15 and LARC RP-46 polyimides in terms of its better processability and mechanical performance.Article Citation - WoS: 17Citation - Scopus: 18Development of an Ionic Liquid Based Method for the Preparation of Albumin Nanoparticles(John Wiley and Sons Inc., 2018) Demirkurt, Begüm; Akdoğan, YaşarAlbumin based nanocarriers have been widely used in drug delivery studies. Here, we developed a water-in-ionic liquid (IL) emulsion-like method to prepare bovine serum albumin (BSA) nanoparticles as alternative to the traditional organic solvents containing techniques. Conformational changes of albumin induced by the imidazolium based ILs at the water-IL interface triggers the BSA nanoparticle formation. The albumin nanoparticle formation are dependent on the experimental parameters and the hydophobicity of the IL. At pH 9.0, using 1.3%wt of BSA in water/1-butyl-3-methyl imidazolium tetrafluoroborate (BmimBF4) (50/50 mol%) and TX-100/butanol surfactant mixture yields uniformly distributed 200 nm average sized BSA nanoparticles. Different than BmimBF4, using a more hydrophilic IL, EmimBF4 yielded albumin aggregates. Instead, using a more hydrophobic IL, HmimBF4 produced albumin nanoparticles but a non-uniform size distribution was obtained. These results indicate that the ionic liquids called green and designer solvents can be also used to synthesize albumin nanoparticles.Article Citation - WoS: 84Citation - Scopus: 85A Review on Halide Perovskites as Color Conversion Layers in White Light Emitting Diode Applications(John Wiley and Sons Inc., 2018) Güner, Tuğrul; Demir, Mustafa MuammerIn the last decade, halide perovskites have attracted great interest due to many reasons, including their low cost, solution-processability, superior PL properties, broad range of color tunability, color purity, and defect tolerance, among others. They are in increasing demand for a wide range of applications, such as solar cells, light emitting diodes (LEDs), white LEDs (WLED), and lasers. Yellow phosphors have been heavily employed in solid-state lighting, since its illumination by blue yields white light with various optical features, such as high/low CRI, CCT, and luminous efficiency. However, phosphors as pigments are seldom found and are costly material. In this sense, halide perovskites may offer a promising alternative to phosphors for future solid-state lighting. In this study, the synthesis and optical properties of halide perovskites, as well as their application in WLED as a conversion layer are investigated.Conference Object Citation - WoS: 1Citation - Scopus: 2A Case Study on Logging Visual Activities: Chess Game(Springer Verlag, 2006) Ozan, Şükrü; Gümüştekin, ŞevketAutomatically recognizing and analyzing visual activities in complex environments is a challenging and open-ended problem. In this study this task is performed in a chess game scenario where the rules, actions and the environment are well defined. The purpose here is to detect and observe a FIDE (Fédération International des Ėchecs) compatible chess board, generating a log file of the moves made by human players. A series of basic image processing operations have been applied to perform the desired task. The first step of automatically detecting a chess board is followed by locating the positions of the pieces. After the initial setup is established every move made by a player is automatically detected and verified. Intel® Open Source Computer Vision Library (OpenCV) is used in the current software implementation.Conference Object Computational Sciences Learning Project for Pre-University Students(Springer Verlag, 2007) İnceoğlu, Mustafa Murat; Aslan, Burak GalipIt is quite useful for high school students to study on computational sciences, especially for those who are planning to have a higher education in engineering. This paper proposes a pilot study on 9th and 10 th grade students for teaching them the basic aspects of computer sciences. This study focuses on a schedule consisting two consecutive courses - first one theoric and the second one is applied - for student volunteers from science high schools.Conference Object Citation - WoS: 6Citation - Scopus: 8A Cluster-Based Dynamic Load Balancing Middleware Protocol for Grids(Springer Verlag, 2005) Erciyeş, Kayhan; Payli, Reşat ÜmitWe describe a hierarchical dynamic load balancing protocol for Grids. The Grid consists of clusters and each cluster is represented by a coordinator. Each coordinator first attempts to balance the load in its cluster and if this fails, communicates with the other coordinators to perform transfer or reception of load. This process is repetaed periodically. We show the implementation and analyze the performance and scalability of the proposed protocol.Conference Object Citation - WoS: 4Citation - Scopus: 4Merging Clustering Algorithms in Mobile Ad Hoc Networks(Springer Verlag, 2005) Dağdeviren, Orhan; Erciyeş, Kayhan; Çokuslu, DenizClustering is a widely used approach to ease implementation of various problems such as routing and resource management in mobile ad hoc networks (MANET)s. We first look at minimum spanning tree(MST) based algorithms and then propose a new algorithm for clustering in MANETs. The algorithm we propose merges clusters to form higher level clusters by increasing their levels. We show the operation of the algorithm and analyze its time and message complexities.Conference Object Citation - Scopus: 3Taylor Series Approximation for Low Complexity Semi-Blind Best Linear Unbiased Channel Estimates for the General Linear Model With Applications To Dtv(IEEE Computer Society, 2004) Pladdy, Christopher; Nerayanuru, Sreenivasa M.; Fimoff, Mark; Özen, Serdar; Zoltowski, MichaelWe present a low complexity approximate method for semi-blind best linear unbiased estimation (BLUE) of a channel impulse response vector (CIR) for a communication system which utilizes a periodically transmitted training sequence, within a continuous stream of information symbols. The algorithm achieves slightly degraded results at a much lower complexity than directly computing the BLUE CIR estimate. In addition, the inverse matrix required to invert the weighted normal equations to solve the general least squares problem may be precomputed and stored at the receiver. The BLUE estimate is obtained by solving the general linear model, y = Ah + w + n, for h, where w is correlated noise and the vector n is an AWGN process, which is uncorrelated with w. The solution is given by the Gauss-Markoff Theorem as h = (A TC(h) -1A) -1 A TC(h) -1y. In the present work we propose a Taylor series approximation for the function F(h) = (A TC(h) -1A) -1 A TC(h) -1y where, F: R L → R L for each fixed vector of received symbols, y, and each fixed convolution matrix of known transmitted training symbols, A. We describe the full Taylor formula for this function, F (h) = F (h id + ∑ |α|≥1(h - h id) α (∂/∂h) α F(h id) and describe algorithms using, respectively, first, second and third order approximations. The algorithms give better performance than correlation channel estimates and previous approximations used at only a slight increase in complexity. The linearization procedure used is similar to that used in the linearization to obtain the extended Kalman filter, and the higher order approximations are similar to those used in obtaining higher order Kalman filter approximations,Article Citation - WoS: 21Citation - Scopus: 23Activated Carbon Adsorption of Fuel Oxygenates Mtbe and Etbe From Water(Springer Verlag, 2009) İnal, Fikret; Yetgin, Senem; Aksu, Gülsüm T.; Şimşek, Selvi; Sofuoğlu, Aysun; Sofuoğlu, Sait CemilThe aqueous phase adsorption of fuel oxygenates methyl tertiary butyl ether (MTBE) and ethyl tertiary butyl ether (ETBE) onto commercially available granular activated carbon (GAC; Norit GAC 1240) was investigated in a batch system at 27°C. The oxygenate concentrations were determined by headspace gas chromatography/mass spectrometry analyses. The experimental data were used with four two-parameter isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich) and two kinetic models (pseudo first-order and pseudo second-order) to determine equilibrium and kinetic parameters. Considering the correlation coefficient and root mean square error, Dubinin-Radushkevich isotherm showed better fit with the equilibrium data for MTBE. However, the performances of Langmuir and Dubinin-Radushkevich models were comparable for ETBE. The adsorption capacities were calculated as 5.50 and 6.92 mg/g for MTBE and ETBE, respectively, at an equilibrium solution concentration of 1 mg/L using Dubinin-Radushkevich isotherm. The differences between the model predictions and experimental data were similar for the pseudo first-order and pseudo second-order kinetic models. Gibbs free-energy changes of adsorption were found to be -22.59 and -28.55 kJ/mol for MTBE-GAC and ETBE-GAC systems, respectively, under the experimental conditions studied.