Gebze Institute of Technology ) is one of two institutes of technology founded in Turkey. It is a university for undergraduate and graduate studies and research activities located in a specifically selected area in Gebze, one of the most industrialized regions of the Marmara Region. Wikipedia.
Kucukmehmetoglu M.,Gebze Institute of Technology
Journal of Hydrology | Year: 2012
In the context of transboundary issues, this paper introduces a composite water resources allocation approach that integrates both game theory and Pareto frontier concepts over the case of the Euphrates and Tigris Rivers. The proposed approach searches for an acceptable and viable solution set over the Pareto Frontier Surface via game theory based rationality constraints. For this purpose, the used base model is the Euphrates and Tigris River Basin Model, which is a linear programming model maximizing net economic benefits while optimally allocating scarce water resources in the basin. Results indicate that game theory based strategies and associated constraints provide a determinative backbone for an efficient and effective use of generated Pareto Frontier Surfaces. Additionally, estimated marginal values imply that the upstream countries have upper hand positions regarding their geographic and climatic contexts. After all the generation schemes, it appears that Turkey is the critical partner for inclusion into any form of coalition in the Euphrates and Tigris River Basin. © 2012 Elsevier B.V.
Koseoglu-Imer D.Y.,Gebze Institute of Technology
Desalination | Year: 2013
The effects of evaporation temperature on properties and filtration performances of polysulfone membrane were investigated with a series of experiments. Membranes were fabricated by phase inversion process at five different evaporation temperatures (25 ± 0.4, 35 ± 0.6, 45 ± 0.5, 55 ± 0.5 and 65 ± 0.6 °C). The resulted membranes were characterized by water permeability, MWCO (molecular weight cut-off), AFM, porosity, contact angle and SEM analyses and tested for filtration performances by using a model dye solution (reactive orange 16-RO16) and a real dye-bath textile wastewater. The pore size and density onto the membrane surface become smaller and the surface roughness, porosity, permeability and MWCO values of membranes considerably decreased with the increasing of evaporation temperature. At the pretreatment filtration experiments, the flux values of membranes decreased largely with the increase of the evaporation temperature while the removal efficiencies for color, COD and conductivity parameters increased. At the membrane fouling analysis, the flux reduction ratios (FRR), the filtration (Rt) and fouling (Rf) resistances and the reusable performances of membrane changed directly proportional with roughness, porosity and pore size characteristics of membranes. At the nanofiltration step (NF-270 membrane), the moderate color, chemical oxygen demand (COD) and conductivity removal were showed at permeate of PS-65 membrane (the membrane fabricated at 65 ± 0.6 °C). © 2013 Elsevier B.V.
Bayrakdar H.,Gebze Institute of Technology
Journal of Magnetism and Magnetic Materials | Year: 2011
We have investigated the electromagnetic (EM) characteristics of Co xMn1-xFe2O4 spinel ferrite (where x=0.0, 0.5 and 1.0) nanoparticles (NPs)/paraffin nanocomposite material at 820 GHz. CoxMn1-xFe2O4 NPs have been synthesized by cetyltrimethylammonium assisted hydrothermal route using NaOH. A variation in complex dielectric permittivity and magnetic permeability at room temperature with frequency in the range 820 GHz has been studied. Particles showed phase purity and crystallinity in powder X-ray diffraction (XRD) analysis. At the same time, CoxMn1-xFe2O 4 NPs demonstrated a spinel cubic structure from XRD results. A reflection loss of -46.60 dB was found at 10.5 GHz for an absorber thickness of 2 mm. CoxMn1-xFe2O4 may be attractive candidates for EM wave absorption materials. © 2011 Elsevier B.V.
Kavut S.,Gebze Institute of Technology
Information Sciences | Year: 2012
We give an efficient exhaustive search strategy to enumerate 6 × 6 bijective rotation-symmetric S-boxes (RSSBs) having nonlinearity 24, which is found to be the maximum nonlinearity within the class of 6 × 6 bijective RSSBs. It is shown that there are 3072 RSSBs achieving the cryptographic properties of the inverse function over GF(2 6), i.e., nonlinearity 24, differential uniformity 4, and algebraic degree 5, such that among them there are only four which are not affine-equivalent. Among these four RSSBs, we find a non-affine transformation under which the cryptographic properties of the inverse function are invariant. Then, we define the generalized classes of k-RSSBs as the polynomials of GF(2 n) with coefficients in GF(2 k), where k divides n. Moreover, motivated by the fact that RSSBs are symmetric under a special permutation, we classify all possible permutations up to the linear equivalence of S-boxes that are symmetric under them. © 2012 Elsevier Inc. All rights reserved.
Melikoglu M.,Gebze Institute of Technology
Renewable and Sustainable Energy Reviews | Year: 2014
Shale gas revolution that took place in the United States at the beginning of the 21st century has still been shaping our global fossil fuel market. In 2012, the U.S. has surpassed Russia in natural gas production for the first time since 1982. At the same year, annual average U.S. Henry hub natural gas spot price decreased to $2.75 per million BTU, which was $8.69 per million BTU in 2005. In 2013, proved shale gas reserves of the world is estimated at nearly 2.7 trillion cubic metres (tcm) and unproved resources at staggering 203.9 tcm. As a result, there is a global rush to develop most of this resource as possible. However, shale gas is no miracle fuel. It has been suggested that its effects on the environment could be worse than conventional natural gas. Fugitive methane emissions, groundwater pollution, and increased seismicity are amongst the most important potential environmental side effects. There is also concern about the accuracy of resource potential estimations due to lack of data and specifically designed shale gas reservoir models. Nonetheless, the analysis in this study clearly showed that without developing global shale gas resources we have to consume 66% of our proved natural gas reserves to supply the demand till 2040. This would make most of the world natural gas importers, and rules of economy dictate that limited supply and increasing demand would skyrocket natural gas prices. Therefore, shale gas resource development is not an option but a must for the continuance of our global energy market and economy. © 2014 Elsevier Ltd.