280 results
Search Results
Now showing 1 - 10 of 280
Article Citation - WoS: 29Citation - Scopus: 31Computing Marginal and Joint Birnbaum, and Barlow-Proschan Importances in Weighted-k-out-of-n< Systems(Pergamon-elsevier Science Ltd, 2014) Eryilmaz, Serkan; Bozbulut, Ali RizaA weighted-k-out-of-n:G system is a system that consists of n binary components, each with its own positive weight, and operates only when the total weight of working components is at least k. Such a structure is useful when the components have different contributions to the performance of the entire system. This paper is concerned with both marginal and joint Birnbaum, and Barlow-Proschan (BP) importances of the components in weighted- k-out-of-n:G systems. The method of universal generating function is used for computing marginal and joint Birnbaum importances. The method for computing BP-importance is based on a direct probabilistic approach. Extensive numerical calculations are presented. By the help of these calculations and illustrations, it is possible to observe how the marginal and joint importances change with respect to the weights of components. (C) 2014 Elsevier Ltd. All rights reserved.Article Citation - WoS: 9Citation - Scopus: 9Thermally Stimulated Current Measurements in Undoped Ga3inse4< Single Crystals(Pergamon-elsevier Science Ltd, 2011) Isik, M.; Işık, Mehmet; Gasanly, N. M.; Işık, Mehmet; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringThe trap levels in nominally undoped Ga3InSe4 crystals were investigated in the temperature range of 10-300 K using the thermally stimulated currents technique. The study of trap levels was accomplished by the measurements of current flowing along the c-axis of the crystal. During the experiments we utilized a constant heating rate of 0.8 K/s. Experimental evidence is found for one hole trapping center in the crystal with activation energy of 62 meV. The analysis of the experimental TSC curve gave reasonable results under the model that assumes slow retrapping. The capture cross-section of the trap was determined as 1.0 x 10(-25) cm(2) with concentration of 1.4 x 10(17) cm(-3). (C) 2011 Elsevier Ltd. All rights reserved.Conference Object Citation - WoS: 2Citation - Scopus: 2Radiation Source Terms of Myrrha Reactor Components and Equipment(Pergamon-elsevier Science Ltd, 2016) Celik, Yurdunaz; Stankovskiy, Alexey; Engelen, Jeroen; Van den Eynde, Gert; Sarer, Basar; Sahin, SumerIn-vessel structural components of nuclear reactors are subject to prompt and residual neutron and photon activation. The MYRRHA fast spectrum facility, when operated in sub critical mode, suffers additional activation due to a wide range of energetic particles produced in the interactions of 600 MeV-primary protons with matter. The purpose of this work was to assess the source term (activation, heating and induced radiation level) of ex core equipment and components located inside the reactor vessel. Numerous stainless steel samples uniformly distributed inside the vessel have been used to simulate the activation of equipment in order to take into account the perturbation of the neutron spectrum caused by structural materials of components and equipment. The calculated quantities were prompt and residual activation, heating, radiation dose and radiation damage. The calculations were carried out with the ALEPH2 depletion code which invokes the MCNPX code for radiation transport. Copyright (C) 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.Article Citation - WoS: 64Vision 2023: Feasibility Analysis of Turkey's Renewable Energy Projection(Pergamon-elsevier Science Ltd, 2013) Melikoglu, MehmetElectricity consumption of Turkey at the year 2023 is estimated to be around 530,000 GWh. Turkey plans to supply 30% or 160,000 GWh of this demand from renewable energy sources according to the recently avowed government agenda Vision 2023. However, the current installed renewable energy capacity is around 60,000 GWh. Detailed literature analysis showed that only wind and solar energy potential in Turkey can solely supply this demand. In this study, two different scenarios were generated to analyse the cost and environmental impacts of supplying this demand. Scenario 1, which is derived from the official Vision 2023 targets, suggests supplying this demand from wind, solar, geothermal energy and hydropower. The total projected cost based on Scenario 1 is estimated to be $31.000 billion and annual greenhouse gas emissions of 1.05 million tonnes of CO2 equivalent. According to Scenario 2 or the contrary setup it is assumed that the required demand gap could not be supplied from new renewable energy investments but equally from coal and natural gas. The projected cost is estimated to be around $8.000 billion and annual greenhouse gas emissions at appalling 71.30 million tonnes of CO2 equivalent. Assuming carbon tax at the year 2023 to be $50 per tonne of CO2 emitted, supplying the demand from renewable energy sources according to Scenario 1 would generate savings worth nearly $2.175 billion from environmental taxes annually. Thus, making the payback time of the renewable energy investments less than 15 years. (C) 2012 Elsevier Ltd. All rights reserved.Article Citation - WoS: 23Citation - Scopus: 22Improved Global Robust Stability Criterion for Delayed Neural Networks(Pergamon-elsevier Science Ltd, 2007) Singh, VimalA criterion for the uniqueness and global robust stability of the equilibrium point of interval Hopfield-type delayed neural networks is presented. The criterion is a marked improvement over a recent criterion due to Cao, Huang and Qu. (c) 2005 Elsevier Ltd. All rights reserved.Conference Object Citation - WoS: 67Citation - Scopus: 81Seasonal and Yearly Wind Speed Distribution and Wind Power Density Analysis Based on Weibull Distribution Function(Pergamon-elsevier Science Ltd, 2015) Bilir, Levent; Imir, Mehmet; Devrim, Yilser; Albostan, AyhanWind energy, which is among the most promising renewable energy resources, is used throughout the world as an alternative to fossil fuels. In the assessment of wind energy for a region, the use of two-parameter Weibull distribution is an important tool. In this study, wind speed data, collected for a one year period between June 2012 and June 2013, were evaluated. Wind speed data, collected for two different heights (20 m and 30 m) from a measurement station installed in Atihm University campus area (Ankara, Turkey), were recorded using a data logger as one minute average values. Yearly average hourly wind speed values for 20 m and 30 m heights were determined as 2.9859 m/s and 3.3216 m/s, respectively. Yearly and seasonal shape (k) and scale (c) parameter of Weibull distribution for wind speed were calculated for each height using five different methods. Additionally, since the hub height of many wind turbines is higher than these measurement heights, Weibull parameters were also calculated for 50 m height. Root mean square error values of Weibull distribution functions for each height, derived using five different methods, show that a satisfactory representation of wind data is achieved for all methods. Yearly and seasonal wind power density values of the region were calculated using the best Weibull parameters for each case. As a conclusion, the highest wind power density value was found to be in winter season while the lowest value was encountered in autumn season. Yearly wind power densities were calculated as 39.955 (W/m(2)), 51.282 (W/m(2)) and 72.615 (W/m(2)) for 20 m, 30 m and 50 m height, respectively. The prevailing wind direction was also determined as southeast for the region. It can be concluded that the wind power density value at the region is considerable and can be exploited using small scale wind turbines. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.Conference Object Citation - WoS: 7Citation - Scopus: 7Synthesis, Characterizations and Investigation of Thermoluminescence Properties of Strontium Pyrophosphate Doped With Metals(Pergamon-elsevier Science Ltd, 2014) Ilkay, L. S.; Ozbayoglu, G.; Yilmaz, A.Strontium pyrophosphate, Sr2P2O7, was synthesized by solid-state synthesis method; the product was co-doped with copper-silver (Cu-Ag), copper-indium (Cu-In) and manganese-praseodymium (Mn-Pr) oxides (CuO, MnO, In2O3, Pr6O11 and AgNO3) by solid-state reaction method. The variation of dopant concentrations was investigated from 0.5 to 15% by weight. In addition to these processes, chemical characterizations of samples and the investigation of thermoluminescence (TLD) properties of strontium pyrophosphate with and without dopants were conducted. For the characterization; powder X-ray Diffraction (XRD) were implemented for phase purity of samples. Fourier Transform Infrared Spectroscopy (FTIR) was used to determine whether the bond structures were affected from the doping or not. Thermoluminescence (TLD) analyses were conducted on strontium pyrophosphate doped with different amounts of dopants for the first time. Glow curves showed that intensities were affected by different amounts of dopants. It can be concluded from that strontium pyrophosphate doped with 7% MnO and 1% Pr6O11 had the most powerful peak intensity around 160 degrees C and dosimetric property for promising application. (C) 2014 Elsevier Ltd. All rights reserved.Article Citation - WoS: 136Citation - Scopus: 187Improving Programming Skills in Engineering Education Through Problem-Based Game Projects With Scratch(Pergamon-elsevier Science Ltd, 2018) Topalli, Damla; Cagiltay, Nergiz ErcilNowadays, programming skills are receiving widespread attention for different age groups alongside occupational education programs to better prepare individuals for their future careers. However, introducing programming concepts in an appropriate manner is a challenge in higher education. The main assumption of this study is that enhancing the classical introduction to programming courses through real-life problem-based game development with Scratch programming environment potentially improves the learners' programming skills and motivation. Accordingly, in this study, during one academic semester period, the Introduction to Programming course for engineering students is enriched up to a certain level through real-life game development projects with Scratch. The students are followed within a four-year period starting from freshman until their graduation. The progress of the students who have taken the Introduction to Programming course in enriched or classical form in the fourth year Senior-project course are evaluated. The results show that by slightly improving the course curriculum through real-life game development projects in the Scratch environment, students' performance on the graduation projects improved significantly. As a conclusion, game-based learning, problem-based learning, visual programming and projects are technologies that can potentially help learners to perform better in the introduction to programming course, in turn affecting their performances in projects.Article Citation - WoS: 7Citation - Scopus: 7Political Interest Across Cultures: the Role of Uncertainty Avoidance and Trust(Pergamon-elsevier Science Ltd, 2022) Kucukkomurler, Sanem; Ozkan, TurkerPrevious studies revealed a negative relationship between uncertainty avoidance tendencies and political interest at the country level. It implies that when there is a tendency to avoid uncertainties, citizens prefer not to be interested in politics. At the same time, there are findings in intergroup relations literature pointing to the intention to deal with uncertainties by participating in political activities (e.g., protests). We wonder whether a moderator, trust, impacts the relationship between uncertainty avoidance and political interest at the cultural level. The results demonstrated that (1) uncertainty is related to a decline in political interest, (2) trust has a moderator effect on the relationship between uncertainty avoidance and political interest, and (3) the moderation effect of trust is unique to the uncertainty avoidance dimension. These results revealed that trust has both enhancive and mitigative functions in the relationship between uncertainty avoidance and political interest.Article Citation - WoS: 70Citation - Scopus: 82The Effect of Uncertainty on Learning in Game-Like Environments(Pergamon-elsevier Science Ltd, 2013) Ozcelik, Erol; Cagiltay, Nergiz Ercil; Ozcelik, Nese SahinConsidering the role of games for educational purposes, there has an increase in interest among educators in applying strategies used in popular games to create more engaging learning environments. Learning is more fun and appealing in digital educational games and, as a result, it may become more effective. However, few research studies have been conducted to establish principles based on empirical research for designing engaging and entertaining games so as to improve learning. One of the essential characteristics of games that has been unexplored in the literature is the concept of uncertainty. This study examines the effect of uncertainty on learning outcomes. In order to better understand this effect on learning, a game-like learning tool was developed to teach a database concept in higher education programs of software engineering. The tool is designed in two versions: one including uncertainty and the other including no uncertainty. The experimental results of this study reveal that uncertainty enhances learning. Uncertainty is found to be positively associated with motivation. As motivation increases, participants tend to spend more time on answering the questions and to have higher accuracy in these questions. (C) 2013 Elsevier Ltd. All rights reserved.
