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Gokek M.,Nide University
International Journal of Hydrogen Energy | Year: 2010

This study presents a techno-economic evaluation on hydrogen generation from a small-scale wind-powered electrolysis system in different power matching modes. For the analysis, wind speed data, which measured as hourly time series in Kirklareli, Turkey, were used to predict the electrical energy and hydrogen produced by the wind-hydrogen energy system and their variation according to the height of the wind turbine. The system considered in this study is primarily consisted of a 6 kW wind-energy conversion system and a 2 kW PEM electrolyzer. The calculation of energy production was made by means of the levelized cost method by considering two different systems that are the grid-independent system and the grid-integrated system. Annual production of electrical energy and hydrogen was calculated as 15,148.26 kWh/year and 102.37 kg/year, respectively. The highest hydrogen production is obtained in January. The analyses showed that both electrical energy and hydrogen production depend strongly on the hub height of wind turbine in addition to the economic indicators. In the grid-integrated system, the calculated levelized cost of hydrogen changes in the range of 0.3485-4.4849 US$/kg for 36 m hub height related to the specific turbine cost. The grid-integrated system can be considered as profitable when the excess electrical energy delivered by system sold to the grid. © 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved. Source


Bahar M.K.,Karamanoglu Mehmetbey University | Soylu A.,Nide University
Physics of Plasmas | Year: 2014

We numerically solve the Schrödinger equation, using a more general exponential cosine screened Coulomb (MGECSC) potential with an electric field, in order to investigate the screening and weak external electric field effects on the hydrogen atom in plasmas. The MGECSC potential is examined for four different cases, corresponding to different screening parameters of the potential and the external electric field. The influences of the different screening parameters and the weak external electric field on the energy eigenvalues are determined by solving the corresponding equations using the asymptotic iteration method (AIM). It is found that the corresponding energy values shift when a weak external electric field is applied to the hydrogen atom in a plasma. This study shows that a more general exponential cosine screened Coulomb potential allows the influence of an applied, weak, external electric field on the hydrogen atom to be investigated in detail, for both Debye and quantum plasmas simultaneously. This suggests that such a potential would be useful in modeling similar effects in other applications of plasma physics, and that AIM is an appropriate method for solving the Schrödinger equation, the solution of which becomes more complex due to the use of the MGECSC potential with an applied external electric field. © 2014 AIP Publishing LLC. Source


Ozcan F.,Nide University
Construction and Building Materials | Year: 2012

In this study, gene expression programming (GEP) formulations for splitting tensile strength (f spt) of the cylinder specimens with 150 mm diameter and 300 mm height using compressive strength (f c) of concrete cube specimens with 150 mm dimension are developed. Two models, called as GEP-I and GEP-II, are developed for predicting f spt by using GEP. The database used in the GEP models is based on experimental data obtained from literature. In the GEP-I model, while f c is used as input variable, f spt is used as output variable. However, in the GEP-II model, as well as f c, water-binder ratio (WB) is used as input variables. The data sets used in training and testing stages are randomly selected among all experimental data. The GEP formulations are also validated with additional experimental data other than the data used in training and testing sets of the GEP models. Experimental f spt results of concrete specimens are compared with GEP formulations, proposed formulations by some national building codes and the developed regression-based formulation results. The results show that GEP formulations have strong potential as a feasible tool for prediction of the f spt from only 150 mm cube f c or WB and 150 mm cube f c of concrete. © 2011 Elsevier Ltd. All rights reserved. Source


Vapur H.,Cukurova University | Bayat O.,Cukurova University | Uurum M.,Nide University
Energy Conversion and Management | Year: 2010

This study discusses a new coal flotation optimization approach. It is conducted using modified flotation parameters and combustible recovery. The experimental work was evaluated in two stages. In the first stage, recoveries (1, 2, 3, 5 and 8 min of flotation times) of Jameson flotation operating parameters were fitted to first-order kinetic model, R = R∞ [1 - exp (-kt)] where R was recovery at t time, R∞ was ultimate recovery and k was the first-order rate constant to draw the time recovery curves in the experimental study. Two parameters, the ultimate recovery (R ∞) and first-order rate constant (k), were then obtained from the model to fit an experimental time recovery curve. A modified flotation rate constant (Km) defined as product of R∞ and k, i.e., Km = R∞ k, and selectivity index (SI) defined as the ratio of the modified rate constant of coal to the modified rate constant of ash (SI)=Km of Coal/Km of Ash), which could be collectively called "modified flotation parameters". It was used to determine of the sub and upper values of operation variables. In the second one, combustible recovery (%) and ash content (%) were used to optimization of the Jameson flotation variables and it was found that d80 = 0.250 mm particle size, 1/1 vegetable oil acids/kerosene ratio, 20% solids pulp density, 0.600 L/min wash water rate and 40 cm downcomer immersion dept could be used to separate efficiently coal from ash. Final concentrate was obtained with 94.83% combustible recovery and 17.86% ash content at optimum conditions after 8 min flotation time. © 2010 Elsevier Ltd. All rights reserved. Source


Compressive strength and splitting tensile strength are both mechanical properties of concrete that are utilized in structural design. This study presents gene expression programming (GEP) as a new tool for the formulations of splitting tensile strength from compressive strength of concrete. For purpose of building the GEP-based formulations, 536 experimental data have been gathered from existing literature. The GEP-based formulations are developed for splitting tensile strength of concrete as a function of age of specimen and cylinder compressive strength. In experimental parts of this study, cylindrical specimens of 150 × 300 mm and 100 × 200 mm in dimensions are utilized. Training and testing sets of the GEP-based formulations are randomly separated from the complete experimental data. The GEP-based formulations are also validated with additional 173 data of experimental results other than the data used in training and testing sets of the GEP-based formulations. All of the results obtained from the GEP-based formulations are compared with the results obtained from experimental data, the developed regression-based formulation and formulas given by some national building codes. These comparisons showed that the GEP-based formulations appeared to well agree with the experimental data and found to be quite reliable. © 2011 Elsevier Ltd. All rights reserved. Source

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