Kajama, Mohammed Nasir | Yıldırım, Yılmaz | Taura, Usman Habu | Grema, Alhaji Shehu | Abdulrahman, Shehu

Article | 2018 | NANO HYBRIDS AND COMPOSITES21 , pp.43 - 52

A dip-coating technique was applied to prepare a selective membrane on a commercial ceramic mesoporous support. Single gas components used for permeance and selectivity were CH4, CO2, H-2, He, N-2, and O-2 (BOC UK) with at least 99.999 (% v/v) purity. The permeances and selectivities were obtained at room temperature and transmembrane pressure differences between 0.05 up to 5.0 barg. Gas permeation experiments showed the permeance of CO2 to be strongly influenced by surface diffusion mechanism. Single gas experiment showed linear flow dependence on the inverse square root of molecular weight at room temperature and 1.0 barg. The sin . . .gle gas selectivities were found to be higher than the ideal Knudsen separation mechanism. The highest CO2/CH4 selectivity value of 24.07 was obtained at 0.7 barg and room temperature Daha fazlası Daha az

Çakmakçı, Mehmet | Kınacı, Cumali | Bayramoğlu, Mahmut | Yıldırım, Yılmaz

Article | 2010 | Expert Systems with Applications37 ( 2 ) , pp.1369 - 1373

Effluent iron concentration is an important water quality criterion used for the assessment of the performance of rapid sand filters, in addition to other criteria. This study deals with the prediction of effluent iron concentrations by adaptive neuro-fuzzy (ANFIS) model with input parameters including filter hydraulic loading rate, influent iron concentration, bed porosity and operation time. With trying various types of membership functions, two rule base generation methods, namely subtractive clustering and grid partition were used for a first order Sugeno type inference system. Models were evaluated using root mean squared error . . . (RMSE), index of agreement (IA) and R2 as statistical performance parameters. The fit between experimental results and model outputs showed good agreement for tap water and deionized water; testing RMSE values were 36.33 and 7.66 µg/L, the IA values were 0.996 and 0.971, and R2 values were 0.99 and 0.89, respectively. It was concluded that neuro-fuzzy modeling may be successfully used to predict effluent iron concentration in sand filtration. © 2009 Elsevier Ltd. All rights reserved Daha fazlası Daha az

Yıldırım, Yılmaz | Demircioğlu, Nuhi | Kobya, Mehmet | Bayramoğlu, Mahmut

Article | 2002 | Environmental Pollution118 ( 3 ) , pp.411 - 417

A non-linear simple air-quality model was developed by applying the continuity equation for the air control volume over Erzurum city center and tested using daily average values of SO2 and meteorological data obtained during the winter seasons in Erzurum, Turkey from 1994 to 1998. Model parameters are estimated by non-linear regression analysis. Agreement between model predictions and measured data was found very satisfactory with standard deviations less than 20 µg/m3. © 2002 Elsevier Science Ltd. All rights reserved.

Yıldırım, Yılmaz | Hughes, Ronald

Article | 2003 | Process Safety and Environmental Protection: Transactions of the Institution of Chemical Engineers, Part B81 ( 4 ) , pp.257 - 261

In this investigation, the preparation and gas selectivity characteristics of an 'ultrafine' composite ceramic membrane are reported. A dip-coating technique was used to prepare a thin selective membrane on a commercially available ceramic macroporous filter (SCT, France). The permeabilities of H2, N2 and CO2 were measured at temperatures of 25-470°C and average pressures of 1-2 bar. The separation of CO2/N2 binary mixtures was also performed. The separation factors for CO2 were found to be higher than that of the Knudsen separation mechanism at room and high temperature. The potential applications of these membranes to CO2 separati . . .on at these temperatures are discussed on the basis of measured selectivity values Daha fazlası Daha az

Yıldırım, Yılmaz | Hughes, Ronald

Article | 2002 | PROCESS SAFETY AND ENVIRONMENTAL PROTECTION80 ( B3 ) , pp.159 - 164

Catalytic inorganic membrane preparation and the catalytic oxidation of o-xylene contained in air streams on catalytic membrane tubes are presented in this study. Boehmite prepared sols were deposited onto porous alumina tubes from the outside using a filtration coating technique. The coatings were characterized by nitrogen gas permeations at the same temperatures used for the o-xylene experiments. Single gas permeabilities indicated a best separation factor for the modified membrane for H-2/N-2 of 3.6, which is very close to the Knudsen value. Pt loading was estimated as 1.6%w/w based on membrane material weight by using both weigh . . .ing and atomic absorption spectrophotometry (AAS) methods. O-ylene catalytic oxidation of o-xylene contained in air streams with concentrations between 0.146-0.220% (v/v) was carried out in a catalytic membrane reactor at temperatures between 150-290degreesC and 97% conversion was achieved for 0.146% o-xylene in air at a temperature of 285degreesC Daha fazlası Daha az

Özdemir, Kadir | Yıldırım, Yılmaz | Toröz, İsmail | Uyak, Vedat

Article | 2015 | Asian Journal of Chemistry27 ( 3 ) , pp.984 - 990

This research developed models using multiple linear regression analysis for the prediction of trihalomethane formation in coagulated Istanbul drinking water sources. The power-law model (model 1), using only ?UV272 as the designed parameter, proved the best model to describe the formation of trihalomethane. The other model (model 2), included pH, total organic carbon, chlorine dosages, ultraviolet absorbance at 254 nm (UV254), specific ultraviolet absorbance (SUVA) and differential absorbance at 272 nm (?UV272). The root-meansquare error (RMSE), normalization mean square error (NMSE), regression coefficient (R2) and index of agreem . . .ent (IA) were used as statistical variables to evaluate the model performance. The better prediction results were obtained by model 1 for root-mean-square error, normalization mean square error, R2 and index of agreement as 9.14, 0.015, 0.95 and 0.99, respectively. © 2015, Chemical Publishing Co. All rights reserved Daha fazlası Daha az

Yıldırım, Yılmaz | Bayramoğlu, Mahmut | Hasıloğlu, Samet

Article | 2003 | Fresenius Environmental Bulletin12 ( 10 ) , pp.1173 - 1179

Air pollution continues to be a major problem in many countries. Mathematical models are useful in relating emissions to air quality under a variety of meteorological conditions and source emission concentrations over an urban area. Meanwhile, the forecasting capability of sophisticated models is limited to very large and complex terrains. In this study, an adaptive neuro-fuzzy logic method has been developed to estimate the impact of meteorological factors on SO2 pollution levels. The model satisfactorily forecasts the trends of SO2 concentration levels with a performance between 78-90%.

Yıldırım, Yılmaz | Bayramoğlu, Mahmut

Article | 2006 | Chemosphere63 ( 9 ) , pp.1575 - 1582

Air pollution is a growing problem arising from domestic heating, high density of vehicle traffic, electricity production, and expanding commercial and industrial activities, all increasing in parallel with urban population. Monitoring and forecasting of air quality parameters in the urban area are important due to health impact. Artificial intelligent techniques are successfully used in modelling of highly complex and non-linear phenomena. In this study, adaptive neuro-fuzzy logic method has been proposed to estimate the impact of meteorological factors on SO2 and total suspended particular matter (TSP) pollution levels over an urb . . .an area. The model forecasts satisfactorily the trends in SO2 and TSP concentration levels, with performance between 75-90% and 69-80 %, respectively. © 2005 Elsevier Ltd. All rights reserved Daha fazlası Daha az

Yıldırım, Yılmaz

Article | 2010 | Fresenius Environmental Bulletin19 ( 7 ) , pp.1320 - 1327

In this study, an adaptive neuro-fuzzy logic method has been proposed to estimate roadside NO2 concentration levels. In the analysis, data from summer and winter seasons were modeled separately and five statistical measures, namely, RMSE, IA, R2, NMSE and FB, were used for modeling evaluation. The available data (N=5797) for 2003 were divided into three categories: training, testing and checking, to set up the ANFIS model. The model was trained using 4923 data with 13 input variables consisting of air quality and meteorological data. Summer season data set (between July and August, N=361) and winter season data set (between December . . . and February, N=361) have been separately used for prediction (testing) purposes. In general, RMSE (4.78 and 4.53), NMSE (0.029 and 0.026) and FB (0.03 and 0.01) values are low but IA (0.96 and 0.98) and R2 (0.92 and 0.95) are reasonably high enough to predict the observed values for winter and summer season test data, respectively. In addition, the FOEX values show that the model slightly under-predicts for all input parameters. Overall, the statistical measures confirm the adequacy of the model for predicting NO2 levels in M25 Roadside for winter and summer season test data. © by PSP Daha fazlası Daha az

Altın, Süreyya | Alemdar, Sonay | Altın, Ahmet | Yıldırım, Yılmaz

Article | 2011 | Separation Science and Technology46 ( 5 ) , pp.754 - 764

Selective removal of cadmium from wastewaters is very important, because cadmium is toxic for the environment and for human health. This work is a comprehensive study on the selective removal of Cd(II) from aqueous solutions by using a co-current flow flat sheet supported liquid membrane system. 4.4 × 10-4M Cd(II) concentration was used as a feed solution in the experiments. Toluene containing Aliquat 336 was used as the membrane liquid in the membrane system. Parameters such as the properties of feed and stripping solutions, carrier concentration, and flow rate, which have roles in transport of Cd(II) ions, were optimized. The effi . . .ciency of the system is expressed in terms of permeability and flux values, and transport efficiency. The optimum process conditions for the Cd(II) transport are experimentally found as follows: The feed solution as 2 M HCl, the carrier concentration as 0.1 M Aliquat 336, the stripping solution as 0.06 M EDTA, and the flow rates for the feed and stripping solutions as 50 mL/min and 80 mL/min, respectively. Under these conditions, the Cd(II) transport efficiency is found to be 82%. © Taylor & Francis Group, LLC Daha fazlası Daha az

Uyar, Güray | Ören, Muhammet | Yıldırım, Yılmaz | Öncel, Salim

Article | 2008 | Environmental Forensics9 ( 4 ) , pp.350 - 363

This article describes the first attempt to study the concentration of seven element (Fe, Pb, Ni, Cr, Cu, Co, and As) contaminations in the vicinity of the Eregli Iron and Steel Plant (ERDEMIR) by analysis of two pleurocarpic moss species (Hypnum cupressiforme and Scleropodium purum). Samples of H. cupressiforme were collected from May 2003 to October 2004. Unwashed, dried samples were digested with HNO3/HClO4, and the concentrations of heavy metals were determined by graphite-furnace atomic absorption spectrometry (GFAAS). In the region, general orders of heavy metal content in samples of mosses were determined as follows: Fe > Pb . . .> Cr > Ni > Cu > Co > As. Comparisons were made between the two moss species for those elements presents at different concentrations and regression analysis were made to see interspecies relationship. H. cupressiforme and S. purum are significantly correlated for only Fe (P < 0.01) having Pearson's correlation coefficient as 0.93, indicating interspecies calibration for Fe. The ratios (Hc/Sp) were relatively better correlated with 1/Sp for As than for other metals, suggesting a saturation effect in H. cupressiforme for As. The deposition of metals due to the operation of the steel plant has been established and could be further monitored. Such information could be useful for forensic studies aiming to apportion between different possible sources of those metals. Copyright © Taylor & Francis Group, LLC Daha fazlası Daha az

Kobya, Mehmet | Demirbaş, Erhan | Demircioğlu, Nesli | Yıldırım, Yılmaz | Yıldız, Şevki Yalçın

Article | 2004 | Desalination160 ( 3 ) , pp.253 - 262

Coupled transport of thiocyanate ions through a liquid membrane containing quaternary ammonium chloride salts in chloroform was examined. The influences of the carrier type in the membrane phase on the coupled transport of thiocyanate ions were investigated. The kinetics of the coupled transport were analyzed in the formalism of two consecutive irreversible first-order reactions and the kinetic parameters (k1d, k2m, k2a, Rmmax, tmax, Jdmax, Jamax,) were also calculated. For the coupled transport of thiocyanate ions, quaternary ammonium chloride salts having different carbon atom numbers (Cn) used as carriers were found to increase t . . .hiocyanate ions transport efficiency with increasing carbon atom numbers. Tetradecyl trimethylammonium chloride (TDTMACl), hexadecyl trimethylammonium chloride (HDTMACl), and tetraoctyl ammonium chloride (TOACl) were found to be the most effective carrier types for transport of thiocyanate ions when Cn is greater than 16. The activation energies for maximum membrane entrance and exit fluxes were calculated as 32.45 kJ/mol and 34.75 kJ/mol, respectively. The values of the activation energy indicate that the process is controlled by species diffusion Daha fazlası Daha az