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Citation - Scopus: 19
Advanced Sensor and Detection Materials
(Wiley Blackwell, 2014) Tiwari A.; Demir, M.M.
Presents a comprehensive and interdisciplinary review of the major cutting-edge technology research areas-especially those on new materials and methods as well as advanced structures and properties-for various sensor and detection devices. The development of sensors and detectors at macroscopic or nanometric scale is the driving force stimulating research in sensing materials and technology for accurate detection in solid, liquid, or gas phases; contact or non-contact configurations; or multiple sensing. The emphasis on reduced-scale detection techniques requires the use of new materials and methods. These techniques offer appealing perspectives given by spin crossover organic, inorganic, and composite materials that could be unique for sensor fabrication. The influence of the length, composition, and conformation structure of materials on their properties, and the possibility of adjusting sensing properties by doping or adding the side-groups, are indicative of the starting point of multifarious sensing. The role of intermolecular interactions, polymer and ordered phase formation, as well as behavior under pressure and magnetic and electric fields are also important facts for processing ultra-sensing materials. The 15 chapters written by senior researchers in Advanced Sensor and Detection Materials cover all these subjects and key features under three foci: 1) principals and perspectives, 2) new materials and methods, and 3) advanced structures and properties for various sensor devices. © 2014 Scrivener Publishing LLC. All rights reserved.
Citation - WoS: 4
Citation - Scopus: 8
Advances in Model-Based Testing of Graphical User Interfaces
(Elsevier Academic Press inc, 2017) Belli, Fevzi; Beyazit, Mutlu; Budnik, Christof J.; Tuglular, Tugkan; Tuğlular, Tuğkan; Bilgisayar Mühendisliği Bölümü
Graphical user interfaces (GUIs) enable comfortable interactions of the computer-based systems with their environment. Large systems usually require complex GUIs, which are commonly fault prone and thus are to be carefully designed, implemented, and tested. As a thorough testing is not feasible, techniques are favored to test relevant features of the system under test that will be specifically modeled. This chapter summarizes, reviews, and exemplifies conventional and novel techniques for model-based GUI testing.
Citation - Scopus: 0
AMWC 2013: Advanced Materials World Congress (izmir, Turkey, September 16-19, 2013)
(2013) Demir, M.M.
[No abstract available]
Citation - WoS: 12
Citation - Scopus: 14
Anomalous transmittance of polystyrene-ceria nanocomposites at high particle loadings
(Royal Soc Chemistry, 2013) Parlak, Onur; Demir, Mustafa M.; Demir, Mustafa
Optical nanocomposites based on transparent polymers and nanosized pigment particles have usually been produced at low particle concentrations due to the undesirable optical scattering of the pigment particles. However, the contribution of the particles to many physical properties is realized at high concentrations. In this study, nanocomposites were prepared with transparent polystyrene (PS) and organophilic CeO2 nanoparticles using various compositions in which the particle content was up to 95 wt%. The particles, capped by 3-methacryloxypropyltrimethoxysilane (MPS), were dispersed into PS and the transmittance of the spin-coated composite films was examined over the UV-visible region. When the particle concentration was <20 wt%, the transmittance of the films showed a first-order exponential decay as the Rayleigh scattering theory proposes. However, a positive deviation was observed from the decay function for higher particle contents. The improvement in transmittance may be a consequence of interference in the multiple scattering of light by the quasi-ordered internal microstructure that gradually develops as the particle concentration increases.
Citation - Scopus: 4
An architecture for verification of access control policies with multi agent system ontologies
(2009) Tekbacak, F.; Tuglular, T.; Dikenelli, O.; Tuğlular, Tuğkan; Bilgisayar Mühendisliği Bölümü
Multi-agent systems (MAS) which communicate with intra-domain and inter-domain agent platforms have access control requirements. Instead of a central mechanism, a fine-graned access control mechanism could have been applied to MAS platforms. This paper emphasizes MAS-based domain and security ontologies with XACML-based access control approach for MAS platforms. The domain dependent behaviour and access control parameters in agent ontologies could be combined within a common XACML policy document that is used through different MAS applications. Agent-based access control requirements and common XACML policy documents should be consistent to enforce policies for MAS. To obtain this condition, the translation of organizational policies and platform based policies have to be considered in detail and the verified policy features have to be enforced in MAS to provide access for resources. © 2009 IEEE.
Citation - Scopus: 6
Asthma in the context of global alliance against respiratory diseases (GARD) in Turkey
(AME Publishing Company, 2018) Yorgancioğlu,A.; Gemicioglu,B.; Ekinci,B.; özkan,Z.; Bayram,H.; Ergan,B.; Köktürk,N.
[No abstract available]
Citation - WoS: 109
Citation - Scopus: 123
Chitosan fiber-supported zero-valent iron nanoparticles as a novel sorbent for sequestration of inorganic arsenic
(Royal Soc Chemistry, 2013) Horzum, Nesrin; Demir, Mustafa M.; Nairat, Muath; Shahwan, Talal; Demir, Mustafa
This study proposes a new sorbent for the removal of inorganic arsenic from aqueous solutions. Monodispersed nano zero-valent iron (nZVI) particles were nucleated at the surface of electrospun chitosan fibers (average fiber diameter of 195 +/- 50 nm) by liquid phase reduction of FeCl3 using NaBH4. The material was characterized using SEM, TGA, XPS, XRD, and FTIR. The diameter of iron nanoparticles was found to vary between 75-100 nm. A set of batch experiments were carried out to elucidate the efficiency of the composite sorbent toward fixation of arsenite and arsenate ions. The ion concentrations in the supernatant solutions were determined using inductively coupled plasma-mass spectrometry (ICP-MS). The results revealed that the chitosan fiber supported nZVI particles is an excellent sorbent material for inorganic arsenic uptake at concentrations ranging from 0.01 to 5.00 mg L-1 over a wide range of pH values. Based on XPS analysis, As(III) was found to undergo oxidation to As(V) upon sorption, while As(V) retained its oxidation state. By virtue of the successful combination of the electrospun fibers' mechanical integrity and the large reactivity of dispersed nZVI particles, the applicability of the resulting sorbent material in arsenic sorption holds broad promise.
Citation - WoS: 11
Citation - Scopus: 11
Controlled surface mineralization of metal oxides on nanofibers
(Royal Soc Chemistry, 2015) Horzum, Nesrin; Mari, Margherita; Wagner, Manfred; Fortunato, Giuseppino; Popa, Ana-Maria; Demir, Mustafa M.; Munoz-Espi, Rafael; Demir, Mustafa
We report a versatile approach for the preparation of metal oxide/polymer hybrid nanofibers by in situ formation of metal oxide nanoparticles on surface-functionalized polymer fibers. Poly (styrene-covinylphosphonic acid) fibers were produced by electrospinning and used as supports for the in situ formation of ceria nanocrystals without further thermal treatment. The crystallization of ceria was induced by the addition of an alkaline solution to fibers loaded with the corresponding precursor. The formation of the inorganic material at the fiber surface was investigated by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The extension of the approach to prepare polymer/titania hybrid nanofibers demonstrates its versatility.
Citation - Scopus: 15
Controlling spontaneous emission of CdSe nanoparticles dispersed in electrospun fibers of polycarbonate urethane
(2009) Demir M.M.; Soyal D.; Ünlü C.; Kuş M.; Özçelik, S.
Luminescent fibrous composite films consisting of submicrometer diameter fibers were prepared by electrospinning of segmented polycarbonate urethane (PCU) in dimethyl formamide and tri-n-octylphosphine oxide (TOPO)-capped CdSe nanocrystals (5 nm in diameter) in toluene. Using a pair of conductive electrodes separated with an air gap, we successfully produced randomly deposited and uniaxially aligned electrospun fibers. The surface structure of the electrospun fibers was studied using atomic force microscopy (AFM) and was compared to the corresponding film prepared by casting. In cast film, tapping mode AFM imaging suggests that hard urethane segments organize into rodlike morphology dispersed in soft polycarbonate. When PCU/CdSe dispersions were subjected to electrospinning, copolymer domains were forced to arrange into lamella along the fiber axis due to elongational flow and high stretching. Molecular orientation in the domains of the composite fibers was confirmed by polarized infrared spectroscopy. We demonstrated that formation of the oriented domains by electrospinning develops a hierarchical structure, which consequently modifies spectral properties because new multiple sharp lines appeared in the photoluminescence (PL) spectra of the fibers. In contrast to randomly deposited fibers, the PL intensity of uniaxially aligned fibers was found to be angle dependent. We propose that the elongated internal structure within the fibers controls the spontaneous emission of CdSe nanoparticles dispersed throughout the electrospun mat. A discussion on the nature of the controlled spontaneous emission is provided. © 2009 American Chemical Society.
Citation - Scopus: 0
Correction to: Enhanced light–matter interaction in a hybrid photonic–plasmonic cavity (Applied Physics A, (2021), 127, 12, (907), 10.1007/s00339-021-05071-x)
(Springer Science and Business Media Deutschland GmbH, 2022) Gökbulut B.; Inanç A.; Topcu G.; Ozcelik S.; Demir M.M.; Inci, M.N.
In this article the statement in the Funding information section was incorrect. The correct Funding information is as follows. ‘Dr Belkıs Gökbulut acknowledges TUBITAK for the financial support provided under Contract Number 120F323’. © The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature 2022.
Citation - Scopus: 79
CsPbBr3 perovskites: Theoretical and experimental investigation on water-assisted transition from nanowire formation to degradation
(American Physical Society, 2018) Akbali B.; Topcu G.; Guner T.; Ozcan M.; Demir M.M.; Sahin, H.
Recent advances in colloidal synthesis methods have led to an increased research focus on halide perovskites. Due to the highly ionic crystal structure of perovskite materials, a stability issue pops up, especially against polar solvents such as water. In this study, we investigate water-driven structural evolution of CsPbBr3 by performing experiments and state-of-the-art first-principles calculations. It is seen that while an optical image shows the gradual degradation of the yellowish CsPbBr3 structure under daylight, UV illumination reveals that the degradation of crystals takes place in two steps: transition from a blue-emitting to green-emitting structure and and then a transition from a green-emitting phase to complete degradation. We found that as-synthesized CsPbBr3 nanowires (NWs) emit blue light under a 254 nm UV source. Before the degradation, first, CsPbBr3 NWs undergo a water-driven structural transition to form large bundles. It is also seen that formation of such bundles provides longer-term environmental stability. In addition theoretical calculations revealed the strength of the interaction of water molecules with ligands and surfaces of CsPbBr3 and provide an atomistic-level explanation to a transition from ligand-covered NWs to bundle formation. Further interaction of green-light-emitting bundles with water causes complete degradation of CsPbBr3 and the photoluminescence signal is entirely quenched. Moreover, Raman and x-ray-diffraction measurements revealed that completely degraded regions are decomposed to PbBr2 and CsBr precursors. We believe that the findings of this study may provide further insight into the degradation mechanism of CsPbBr3 perovskite by water. © 2018 American Physical Society.
Citation - WoS: 12
Citation - Scopus: 17
Design of Polymeric Antiscalants Based on Functional Vinyl Monomers for (Fe, Mg) Silicates
(Amer Chemical Soc, 2017) Topcu, Gokhan; Celik, Asli; Baba, Alper; Demir, Mustafa M.; Demir, Mustafa
Silica/silicate scaling is one of a few detrimental problems that cause high economical loss in the geothermal and petroleum fields. The prevention of silica/silicate has been attempted using antiscalants with functional groups, particularly -NH2; however, metal silicates are commonly found in the fields, and the antiscalants developed thus far are not effective against these compounds. In this work, polymeric antiscalants have been developed by merging two or-snore functional-comonomers consisting of various chelating groups for metal cations. Homo- and copolymers of acrylamide (AM), the sodium salt of vinyl sulfonic acid (VSA), and vinyl phosphonic acid (VPA) were synthesized to examine their antiscaling performance against metal silicate scaling. Lab-scale metal silicates were obtained in a pressured autoclave reactor. The, antiscalants were tested at various dosages (25, 50, and 100 ppm), and their effects were investigated from the leftover decaritates after isolation of the solid precipitates. The polymeric antiscalants were found to be particularly effective against metal silicates and ineffective against simple silica precipitates. Acidic groups may be coordinating the metal cations, which prevents the-formation of precipitates. Among these acidic comonomers; VSA-containing polymers, in particular, increased the solubility-of metal silicates.
Citation - Scopus: 52
Development of molecularly imprinted polymers (MIPs) as a solid phase extraction (SPE) sorbent for the determination of ibuprofen in water
(Royal Society of Chemistry, 2017) Olcer Y.A.; Demirkurt M.; Demir M.M.; Eroglu, A.E.
Ibuprofen is a well-known endocrine disrupter. In this study, highly selective molecularly imprinted polymers (MIPs) with different morphologies were synthesized via precipitation and bulk polymerization of methacrylic acid (MAA) and trimethylolpropane trimethacrylate (TRIM) in the presence of ibuprofen as a template. Non-imprinted polymers (NIPs) were also synthesized via the same procedure in the absence of ibuprofen. Spherical and monolithic MIPs were obtained using different experimental conditions, and the spherical MIP was shown to have better sorption towards ibuprofen. The optimum sample pH, sorbent amount, sample volume, and sorption time were determined to be 8.0, 25.0 mg, 10.0 mL, and 30.0 min, respectively. A methanol water mixture (MeOH:H2O, 80:20, pH 3.0) was employed as an eluent with >97% (±0.8, n = 3) desorption. The MIP demonstrated high selectivity towards ibuprofen in the presence of naproxen and ketoprofen. The validity of the proposed method was checked via spike recovery tests using drinking and tap water samples. The method worked efficiently for both water types, resulting in the recoveries of 97.2% (±0.3, n = 3) and 97.7% (±0.2, n = 3). © 2017 The Royal Society of Chemistry.
Citation - Scopus: 2
Dimensions of polystyrene particles deposited on mica from dilute cyclohexane solution at different temperatures
(2002) Demir M.M.; Erman, B.
Using atomic force microscopy, the height, diameter, and volume of polystyrene particles deposited on mica from dilute cyclohexane solution at different temperatures are determined. Dimensions exhibit a strong temperature dependence. The heights of the deposited particles are only a few atomic diameters, the major dimension being parallel to the mica surface. The number of single polystyrene molecules in a deposited particle cannot be determined directly by atomic force microscopy. However, the maximum number of molecules that may be present in a particle may be estimated. Below 35 °C, the particles possibly consist of single collapsed molecules. This number increases with temperature and becomes as large as about 30 molecules per particle at 80 °C. The volume occupied by a single chain in solvent is calculated as a function of temperature and compared with observed volumes of dry particles on mica. A linear relationship is observed between single chain volumes in solvent and corresponding particle volumes on mica. On the average, the volume of a single chain in solution is 10 times the volume of a dry particle at the corresponding temperature. Fluctuations of chain volumes that are dominant in solution are also present in the volumes of particles deposited and dried on mica.
Citation - WoS: 15
Citation - Scopus: 16
Electrospun amino-functionalized PDMS as a novel SPME sorbent for the speciation of inorganic and organometallic arsenic species
(Royal Soc Chemistry, 2013) Boyaci, Ezel; Horzum, Nesrin; Cagir, Ali; Demir, Mustafa M.; Eroglu, Ahmet E.; Demir, Mustafa
Sol-gel based amine-functionalized SPME fibers (PDMS-weak anion exchanger) were prepared and used for direct mode extraction of dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), and arsenate (As(V)) from aqueous solutions followed by HPLC-ICPMS determination. Two different methods of coating were employed: (i) electrospinning and (ii) dip coating. Electrospinning was used for the first time for preparation of sol-gel based SPME fibers and was found to be superior in terms of extracted amount of arsenicals, coating homogeneity, accessibility of amine groups on the surface, and preparation time for a single fiber. Various parameters such as solution pH, extraction time, agitation speed, extraction temperature, and ionic strength were studied. Optimum extraction conditions were determined as pH of 5.0, extraction time of 30 min, agitation speed of 700 rpm, and extraction temperature of 20 degrees C. Extraction ability of the novel coating decreased by the addition of NaCl as a consequence of the competition between anionic arsenic species and chloride ions for active sites of the weak anion exchanger. This novel sol-gel coating prepared by electrospinning was found to be promising for SPME applications. Vibrational spectroscopy revealed the alignment of PDMS chains by elongational force under electrospinning process. The chain alignment accordingly orients the pendant amino functional groups perpendicular to the fiber surface, which may develop the free active functional groups available to the medium and lead to the enhancement of the extraction performance. Moreover, the proposed coating strategy through electrospinning might be able to break new ground for various applications in analytical chemistry as well as other disciplines.
Citation - WoS: 4
Citation - Scopus: 9
End-to-end security implementation for mobile devices using TLS protocol
(Springer France, 2006) Kayayurt, Baris; Tuglular, Tugkan; Tuğlular, Tuğkan; Bilgisayar Mühendisliği Bölümü
End-to-end security has been an emerging need for mobile devices with the widespread use of personal digital assistants and mobile phones. Transport Layer Security Protocol (TLS) is an end-to-end security protocol that is commonly used on the Internet, together with its predecessor, SSL protocol. By implementing TLS protocol in the mobile world, the advantage of the proven security model of this protocol can be utilized. The main design goals of mobile end-to-end security protocol are maintainability and extensibility. Cryptographic operations are performed with a free library, Bouncy Castle Cryptography Package. The object oriented architecture of proposed end-to-end security protocol implementation makes the replacement of this library with another cryptography package easier. The implementation has been experimented with different cases, which represent use of different cryptographic algorithms.
Citation - Scopus: 8
Enhanced Spontaneous Emission Rate in a Low- Q Hybrid Photonic-Plasmonic Nanoresonator
(American Chemical Society, 2019) Gökbulut B.; Inanç A.; Topcu G.; Unluturk S.S.; Ozcelik S.; Demir M.M.; Inci, M.N.
In this paper, CdTe quantum dots (QDs)-doped single electrospun polymer nanofibers are partially coated with gold nanoparticles to form distinct hybrid photonic-plasmonic nanoresonators to investigate the critical role of the cavity-confined hybrid mode on the modification of the spontaneous emission dynamics of the fluorescent emitters in low-Q photonic cavities. A total enhancement factor of 11.2 is measured via a time-resolved experimental technique, which shows that there is an increase of about three times in the spontaneous emission rate for the QDs-doped gold nanoparticle-decorated nanofibers as they are compared with those uncoated ones. The physical mechanism affecting the spontaneous emission rate of the encapsulated QDs in such a hybrid photonic-plasmonic nanoresonator is explained to be due to regeneration of the mode field in the nanofiber cavity upon the interaction of the dipoles with the surface plasmons of distinctive gold nanoparticles that surround the outer surface of the nanofiber. Copyright © 2019 American Chemical Society.
Citation - WoS: 5
Citation - Scopus: 5
Enhancement of the Spontaneous Emission Rate of Perovskite Nanowires Coupled into Cylindrical Hollow Nanocavities Formed on the Surface of Polystyrene Microfibers
(Amer Chemical Soc, 2019) Goekbulu, Bellus; Inanc, Arda; Topcu, Gokhan; Guner, Tugrul; Demir, Mustafa M.; Inci, M. Naci; Demir, Mustafa
Fluorescent CsPbBr3 nanowires are uniformly integrated into a porous polystyrene matrix in the form of microfibers to investigate the changes in their spontaneous emission rate. Cylindrical hollow nanocavities, ranging from 75 to 160 nm in diameter, are grown on the surface of the polymer microfibers during the fabrication process, which allow coupling light that is emitted from the excited CsPbBr3 nanowires. Time-resolved experiments elucidate that the spontaneous emission rate of the perovskite nanowires is observed to increase by a factor of 4.9, upon coupling of the excited optical modes into the nanocavities, which is demonstrated to be in good agreement with our theoretical calculations.
Citation - Scopus: 4
Experimental and first-principles investigation of Cr-driven color change in cesium lead halide perovskites
(American Institute of Physics Inc., 2019) Ozen S.; Guner T.; Topcu G.; Ozcan M.; Demir M.M.; Sahin, H.
Herein, we report room temperature Cr-doping for all-inorganic perovskites that have attracted great attention in recent years due to their extraordinary optical properties, low cost, and ease of synthesis. Incorporation of Cr 3 + ions into the perovskite crystal lattices is achieved by following a facile route involving an antisolvent recrystallization method at room temperature. It is shown that both Cr-doping and formation of crystals in the CsPbBr x Cl 3 - x phase are provided by increasing the concentration of the CrCl 3 solution. It is also observed that the doping procedure leads to the emergence of three types of distinctive peaks in the PL spectrum originating from CsPbBr x Cl 3 - x domains (476-427 nm), Cr-strained host lattices (515 nm), and midgap states formed by Cr dopants (675-775 nm). It is also found that the Cr-doped perovskites emitting a dark violaceous color change their color to white with a high color rendering index (88) in 30-day time intervals. Easy-tunable optical properties of all-inorganic Cs perovskites indicate their great potential for future optoelectronic device applications. © 2019 Author(s).
Citation - Scopus: 1
Feedback control static scheduling for real-time distributed embedded systems
(2005) Ayav, T.; Sorel, Y.; Ayav, Tolga; Bilgisayar Mühendisliği Bölümü
This paper presents an implementation of feedback control strategy on distributed static scheduling. The static schedule is created taking into account the average execution times of the tasks. Feedback control algorithm handles the unestimated dynamic behaviors in the system and keeps the performance at a desired level. The approach of feedback control supporting static scheduling yields more flexible scheduling, low scheduling overhead and better resource utilization while preserving the realtime constraints. © 2005 IEEE.

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