Sürdürülebilir Yeşil Kampüs Koleksiyonu / Sustainable Green Campus Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7755

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  • Article
    Citation - WoS: 45
    Citation - Scopus: 45
    The First Countrywide Monitoring of Selected Pops: Polychlorinated Biphenyls (pcbs), Polybrominated Diphenyl Ethers (pbdes) and Selected Organochlorine Pesticides (ocps) in the Atmosphere of Turkey
    (Elsevier Ltd., 2018) Kurt Karakuş, Perihan Binnur; Ugranlı Çiçek, Tuğba; Sofuoğlu, Sait Cemil; Çelik, Halil; Güngörmüş, Elif; Gedik, Kadir; Sofuoğlu, Aysun; Ökten, Hatice Eser; Birgül, Aşkın; Alegria, Henry; Jones, Kevin C.
    Atmospheric levels of 43 PCBs, 22 OCPs, and 14 PBDEs were determined in 16 cities at urban and rural sites by passive sampling to generate the first large-scale nationwide dataset of POP residues in Turkey's atmosphere. Sampling campaign was performed from May 2014 to April 2015 with three-month sampling periods at locations on east-west and north-south transects through the country to investigate seasonal and spatial variations, including long range atmospheric transport (LRAT). Factor analysis was conducted to infer on the potential sources. Overall average Σ43PCBs concentration was 108 ± 132 pg/m3. PCB-118 (26.3 ± 44.6 pg/m3) was the top congener, and penta-CBs had the highest contribution with 54.3%. ΣDDTs had the highest annual mean concentration with 134 ± 296 pg/m3 among the OCP groups among which the highest concentration compound was p'p-DDE (97.6 ± 236 pg/m3). Overall average concentration of Σ14PBDEs was 191 ± 329 pg/m3 with the highest contribution from BDE-190 (42%). Comparison of OCPs and PCBs concentrations detected at temperatures which were above and below annual average temperature indicated higher concentrations in the warmer periods, hence significance of secondary emissions for several OCPs and Σ43PCBs, as well as inference as LRAT from secondary emissions. The first nationwide POPs database constructed in this study, point to current use, local secondary emissions, and LRAT for different individual compounds, and indicate the need for regular monitoring. The first country-wide passive sampling of selected POPs showed no unequivocal trends reflecting transitional location of Turkey.
  • Article
    Citation - WoS: 46
    Citation - Scopus: 50
    Investigation of Europium Concentration Dependence on the Luminescent Properties of Borogermanate Glasses
    (Elsevier Ltd., 2017) Gökçe, Melis; Şentürk, Ufuk; Uslu, Deniz K.; Burgaz, Gözde; Şahin, Yüksel; Gökçe, Aytaç Gürhan
    In order to elucidate the effect of europium content on the optical and luminescent properties of borogermanate glasses, a series of Eu3+ doped 30B2O3-40GeO2-(30-x)Gd2O3 glasses with various doping levels (x=1–9 mol%) have been synthesized and studied with transmission, absorption, photoluminescence and decay time measurements. The transmission spectra proved that the title glasses maintained a high transparency about 80% in the 440 to 900 nm region. Based on the absorption spectra, the optical band gaps obtained from Tauc's plot can be narrowed by increasing content of Eu3+. From the photoluminescence spectra, the strongest red emission has been observed from the 5D0→7F2 level of Eu3+ ions in borogermanate glasses. The strongest emission and excitation intensities of Eu3+ ions are at the doping level of x=7 mol% and then these intensities decrease due to concentration quenching. The red to orange ratio (R/O) of 5D0→7F2 to 5D0→7F1 transitions has been investigated to predict the local environment of Eu3+ ions. Judd-Ofelt (J-O) analyses have been performed from the emission spectra. The values of R/O and Ω2 present an increase with increasing doping level, indicating the lower symmetric environment for Eu3+ ions and higher covalency for Eu-O bond. The emission efficiency calculated from J-O theory is 75% at x=2 mol%. The decay time curves of 6P7/2→8S7/2 transition of Gd3+ ions and 5D0–7F2 transition of Eu3+ ions confirm the energy transfer from Gd3+ to Eu3+ ions.
  • Article
    Citation - WoS: 30
    Citation - Scopus: 31
    Esterification of Cetyl Alcohol With Palmitic Acid Over Wo3/Zr-sba-15 and Zr-Sba Catalysts
    (Elsevier Ltd., 2016) Mutlu, Nahide Nuran; Yılmaz, Selahattin
    Tungsten loaded and Zr incorporated SBA-15 catalysts (WO3/Zr-SBA-15 and Zr-SBA-15) were developed for esterification of cetyl alcohol and palmitic acid. The influence of the Zr content, tungsten loading amount, calcination temperature, feed composition and catalyst amount has been studied. Higher tungsten loading decreased the acidity due to formation of WO3 crystals whereas calcination temperature enhanced the acidity by favoring the dispersion of WOx species. Activities of the catalyst changed depending on their amount of Brønsted sites and total number of acid sites. Zr-SBA-15 catalyst which had the highest amount of Brønsted acid sites gave maximum cetyl palmitate yield (63.1%). This catalyst retained its activity up to 3 reuse cycles without significant loss of activity.
  • Article
    Citation - WoS: 89
    Citation - Scopus: 105
    Spatial and Temporal Variations in Atmospheric Vocs, No2, So2, and O3 Concentrations at a Heavily Industrialized Region in Western Turkey, and Assessment of the Carcinogenic Risk Levels of Benzene
    (Elsevier Ltd., 2015) Yılmaz Civan, Mihriban; Elbir, Tolga; Seyfioğlu, Remzi; Kuntasal, Öznur Oğuz; Bayram, Abdurrahman; Doğan, Güray; Yurdakul, Sema; Andiç, Özgün; Müezzinoğlu, Aysen; Sofuoğlu, Sait Cemil; Pekey, Hakan; Pekey, Beyhan; Bozlaker, Ayşe; Odabaşı, Mustafa; Tuncel, Gürdal
    Ambient concentrations of volatile organic compounds (VOCs), nitrogen dioxide (NO2), sulphur dioxide (SO2) and ground-level ozone (O3) were measured at 55 locations around a densely populated industrial zone, hosting a petrochemical complex (Petkim), a petroleum refinery (Tupras), ship-dismantling facilities, several iron and steel plants, and a gas-fired power plant. Five passive sampling campaigns were performed covering summer and winter seasons of 2005 and 2007. Elevated concentrations of VOCs, NO2 and SO2 around the refinery, petrochemical complex and roads indicated that industrial activities and vehicular emissions are the main sources of these pollutants in the region. Ozone concentrations were low at the industrial zone and settlement areas, but high in rural stations downwind from these sources due to NO distillation. The United States Environmental Protection Agency's positive matrix factorization receptor model (EPA PMF) was employed to apportion ambient concentrations of VOCs into six factors, which were associated with emissions sources. Traffic was found to be highest contributor to measured ∑VOCs concentrations, followed by the Petkim and Tupras.Median cancer risk due to benzene inhalation calculated using a Monte Carlo simulation was approximately 4 per-one-million population, which exceeded the U.S. EPA benchmark of 1 per one million. Petkim, Tupras and traffic emissions were the major sources of cancer risk due to benzene inhalation in the Aliaga airshed. Relative contributions of these two source groups changes significantly from one location to another, demonstrating the limitation of determining source contributions and calculating health risk using data from one or two permanent stations in an industrial area.
  • Article
    Citation - WoS: 28
    Citation - Scopus: 38
    Bioconversion of Wheat Bran for Polygalacturonase Production by Aspergillus Sojae in Tray Type Solid-State Fermentation
    (Elsevier Ltd., 2016) Demir, Hande; Tarı, Canan
    Wheat bran was tested as the solid substrate for the tray-type solid-state fermentation (SSF) production of polygalacturonase (PG) enzyme by A. sojae mutant strain - a high-PG activity producer. PG production of A. sojae was found to reduce as the thickness of the substrate increase from 8 mm to 14 mm at 90% relative humidity. An interaction between the thickness of the bed and relative humidity of the environment was determined with the help of experimental design and statistical analysis tools. As a result, the PG activity could be enhanced by 31% as the process conditions optimized. Additionally, 11 mm thickness and 70% relative humidity were selected as the PG production favoring conditions with the maximum PG activity of 298 U/g substrate in tray type of SSF without the addition of any nutritive or inducing supplements into wheat bran. The kinetic study conducted in the trays revealed the presence of reduction in the water activity on the 4th day of the SSF process under stated conditions. The productivity of the process conducted under optimized conditions was 3.41 U/g substrate-1 h-1 for the 4th day of the SSF. © 2015 Elsevier Ltd.
  • Article
    Citation - WoS: 11
    Citation - Scopus: 11
    Calibration of Double Stripe 3d Laser Scanner Systems Using Planarity and Orthogonality Constraints
    (Elsevier Ltd., 2014) Ozan, Şükrü; Gümüştekin, Şevket
    In this study, 3D scanning systems that utilize a pair of laser stripes are studied. Three types of scanning systems are implemented to scan environments, rough surfaces of near planar objects and small 3D objects. These scanners make use of double laser stripes to minimize the undesired effect of occlusions. Calibration of these scanning systems is crucially important for the alignment of 3D points which are reconstructed from different stripes. In this paper, the main focus is on the calibration problem, following a treatment on the pre-processing of stripe projections using dynamic programming and localization of 2D image points with sub-pixel accuracy. The 3D points corresponding to laser stripes are used in an optimization procedure that imposes geometrical constraints such as coplanarities and orthogonalities. It is shown that, calibration procedure proposed here, significantly improves the alignment of 3D points scanned using two laser stripes.
  • Article
    Citation - WoS: 39
    Citation - Scopus: 43
    Synthesis and Humidity Sensing Analysis of Zns Nanowires
    (Elsevier Ltd., 2012) Okur, Salih; Üzar, Neslihan; Tekgüzel, Nesli; Erol, Ayşe; Arıkan, M. Çetin
    ZnS nanowires synthesized by the vapor-liquid-solid (VLS) method and humidity sensing properties of obtained ZnS nanowires were investigated by quartz crystal microbalance (QCM) method and electrical measurements. The synthesized nanowires were exposed to relative humidity (RH) between 22% and 97% under controlled environment. Our experimental results show that ZnS nanowires have a great potential for humidity sensing applications in room temperature operations. © 2010 Elsevier B.V. All rights reserved.
  • Article
    Citation - WoS: 86
    Citation - Scopus: 101
    A Comparative Study of Glottal Source Estimation Techniques
    (Elsevier Ltd., 2012) Drugman, Thomas; Bozkurt, Barış; Dutoit, Thierry
    Abstract: Source-tract decomposition (or glottal flow estimation) is one of the basic problems of speech processing. For this, several techniques have been proposed in the literature. However, studies comparing different approaches are almost nonexistent. Besides, experiments have been systematically performed either on synthetic speech or on sustained vowels. In this study we compare three of the main representative state-of-the-art methods of glottal flow estimation: closed-phase inverse filtering, iterative and adaptive inverse filtering, and mixed-phase decomposition. These techniques are first submitted to an objective assessment test on synthetic speech signals. Their sensitivity to various factors affecting the estimation quality, as well as their robustness to noise are studied. In a second experiment, their ability to label voice quality (tensed, modal, soft) is studied on a large corpus of real connected speech. It is shown that changes of voice quality are reflected by significant modifications in glottal feature distributions. Techniques based on the mixed-phase decomposition and on a closed-phase inverse filtering process turn out to give the best results on both clean synthetic and real speech signals. On the other hand, iterative and adaptive inverse filtering is recommended in noisy environments for its high robustness. © 2011 Elsevier Ltd. All rights reserved.
  • Article
    Citation - WoS: 19
    Citation - Scopus: 22
    Optimization of the Associative Growth of Novel Yoghurt Cultures in the Production of Biomass, Ss-Galactosidase and Lactic Acid Using Response Surface Methodology
    (Elsevier Ltd., 2009) Tarı, Canan; Üstok, Fatma Işık; Harsa, Hayriye Şebnem
    The associative growth of Streptococcus thermophilus 95/2 (St 95/2) and Lactobacillus delbrueckii ssp. bulgaricus 77 (Lb 77) isolated from the Toros mountain region of Turkey was investigated with respect to lactic acid, biomass and β-galactosidase enzyme production using response surface methodology (RSM). The ratio (St 95/2:Lb 77) of the strains and media formulation had significant effect on all responses (p < 0.001). The predicted enzyme activity (2.14 U mL-1), lactic acid (22.50 g L-1) and biomass (7.11 g L-1) production at optimum conditions were very close to the actual experimental values (2.14 U mL-1, 22.94 g L-1 and 7.86 g L-1, respectively). The optimum conditions were to use these cultures in a ratio of 1.66:1.62 (St 95/2:Lb 77) in a medium containing whey (5%), corn steep liquor (4%), potassium phosphate (2%) and peptone (2%) at 43 °C for 8 h. The associative growth provided 6.4% and 39% more β-galactosidase activity and 8.73% and 44% more lactic acid compared with the results obtained using pure St 95/2 and Lb 77 strains, respectively.
  • Article
    Citation - WoS: 53
    Citation - Scopus: 60
    Supercritical Deposition of Pt on Sno2-Coated Al2o3 Foams: Phase Behaviour and Catalytic Performance
    (Elsevier Ltd., 2008) Garrido, G. Incera; Patcas, F. C.; Upper, G.; Türk, M.; Yılmaz, Selahattin; Kraushaar-Czarnetzki, B.
    Deposition and reduction of an organometallic platinum complex from a supercritical Pt(COD)Me2/CO2 solution was carried out to produce Pt/SnO2 catalysts supported on Al2O3 foams for CO oxidation at moderate temperatures. The phase behaviour of the complex in supercritical carbon dioxide was investigated to find the optimum pressure and temperature conditions for the deposition. For the Pt(COD)Me2/CO2 mixture, the melting point decreased with increasing pressure from 378 K at 0.1 MPa to 360 K at 25.6 MPa. Additional investigations showed that the solubility of Pt(COD)Me2 in CO2 increases from 5.9 × 10-4 mol/mol at 11.2 MPa and 313 K to 3.4 × 10-3 mol/mol at 29.6 MPa and 353 K. The supercritical deposition yielded catalysts with highly dispersed platinum nanoparticles of approx. 3 nm having a narrow size distribution and thus, a superior activity towards oxidation of carbon monoxide in comparison to a catalyst prepared by the conventional aqueous impregnation of Pt.