Mühendislik Fakültesi / Faculty of Engineering
Permanent URI for this collectionhttps://hdl.handle.net/11727/1401
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Item An Exergetic Approach to The Age of Universe(2014) Kilkis, Birol I.; https://orcid.org/0000-0003-2580-3910; AAJ-2321-2020Recent finding by Bond et al. (2013) about the age of the star HD 140283 (14.46 +/- 0.8 Gyr) requires us to reconsider the estimates about the age of the universe, namely 13.817 +/- 0.048 Gyr. Their conflicting result is analytically supported by the paper in Int. J. Exergy by Kilkis (2004). This paper, which introduced the Radiating Universe Model (RUM) with exergy flow to an infinitely-sized thermal bath at 0 K, predicted that the age of the universe is 14.885 +/- 0.040 Gyr. It further calculated that Hubble constant is 65.7 km s(-1) Mpc(-1) and the expansion of the universe has been accelerating since the cosmic age of 4.4 Gyr due to a positive, time dependent cosmological number that is slightly decreasing and presently it is 8.8 x 10(-36) s(-2). The exergy flow rate, solved by the lumped-capacitance method, changes with the square of cosmic time and is currently 1.224 x 10(50) erg.s(-1).Item Planning Decisions for Recycling Products Containing Hazardous and Explosive Substances: A Fuzzy Multi-Objective Model(2017) Dinler, Esra; Gungor, ZulalThe rapid development of modern technology leads to the rapid consumption of natural resources, which in turn causes an increasing accumulation of waste materials. Manufacturers must now assume the responsibility for reclamation, recycling and disposal of their products that have reached the end of their life cycles. During the product recycling process, the detection and disposal of explosive substances must be performed with the utmost caution. This study proposes a fuzzy multi-objective linear programming model for use in planning of recycling processes for products that contain hazardous and explosive substances. Application of the proposed model has been carried out in a middle-sized factory, where various products that have completed their life cycles or has become inoperative are delivered to the factory at uncertain times from various warehouses. Results from the proposed model have been obtained using the system data to solve problems on various scales. A hybrid Monte Carlo simulation has been used to obtain Pareto-optimal solutions to solve the model. The planning model is shown to differ from the recycling production planning model in terms of its consideration of the explosion risk and the limitations and goals related to this risk; this model provides considerable flexibility for both the recycling process and the planning decisions taken for this process. (C) 2016 Elsevier B.V. All rights.reserved.Item Traveling Repairmen Problem: A Biogeography-Based Optimization(2022) Uzun, Gozde Onder; Dengiz, Berna; Kara, Imdat; Karasan, Oya EkinTraveling Repairman Problem (TRP), which is also known by names cumulative traveling salesman problem, the deliveryman problem and the minimum latency problem, is a special variant of Traveling Salesman Problem (TSP). In contrast to the minimization of completion time objective of TSP, the desired objective of TRP is to minimize the cumulative latency (waiting time or delay time) of all customers. In this paper, a generalized version of TRP with multi depots and time windows, namely Multi Depot Traveling Repairman Problem with Time Windows (MDTRPTW) is considered. A group of homogeneous repairmen initiate and finish their visit tours at multiple depots. Each customer must be visited exactly by one repairman within their provided earliest end latest times. Being a challenging Nondeterministic Polynomial-hard (NP-hard) optimization problem, exact solution approaches are not expected to scale to realistic dimensions of MDTRPTW. Thus, we propose a biogeography-based optimization algorithm (BBOA) as a metaheuristic approach to solve large size MDTRPTW problems. The proposed metaheuristic is analyzed in terms of solution quality, coefficient of variation as well as computation time by solving some test problems adapted from the related literature. The efficacy of the proposed solution methodology is demonstrated by solving instances with 288 customers within seconds.Item The Inventory of Flood Disasters in Turkey(2022) Gurer, Ibrahim; Ucar, IbrahimTurkey is located both Europe and Asia, and covers an area of 780 580 km(2) including the lakes. Turkey undergoes different types of natural disasters because of its geographical location, geomorphology, and topography. Flooding is the second important natural hazard after earthquakes. A flood inventory of the period extending from 1955 to 2020 having a total of about 3250 events was prepared using a simple computer program based on Excel for easy access to different geomorphologic parameters such as surface areas of river basins, slope, geological structure, vegetative cover, type of precipitation, and the elevation above mean sea level (a.m.s.l) and hydro-meteorological parameters. In the same inventory each flood has been defined with damages on human as lost and injured, size of flooded area and loss of wealth (not exact information for wealth). By categorization of the available data in hand, spatial and time distributions of past flood events were determined. In large basins, negative impacts are more closely related to climatic factors, but in small watersheds, the urbanization along the rivers, internal migration, regional planning, urban drainage infrastructure are more important on negative impacts. In order to prevent the floods and minimize the adverse effects to property, both structural and non-structural solutions are applied in Turkey. Two case studies added to show the solutions.Item Hydropower Outlook of Turkey in 2021(2022) Gurer, IbrahimTurkey is located partly on Europe and also on Asia, and has a surface area of 780 580 km(2) and a population of 84.6 million and electric energy is essential for the everyday life. The annual per capita consumption of electricity is mainly used to measure the prosperity of a nation. The energy use in a country increases not only with population increase but also by improving the living standards of people and industrial development. Turkey being a non-oil-producing country at present, therefore needs to import fossil fuels (like natural gas and fuel oil) as the main source of electric energy. The utilization of fossil fuels for energy production by thermal power plants is one of the main sources of air pollution. The consumption of imported energy sources should be reduced for the environmental, economic, and political reasons. As the electricity need of the country is increasing continuously, more energy from the renewables and national resources must be produced. Hydropower plants (HPPs) provide clean, fast, flexible electricity generation. The amount of electricity that aHPP can produce basically depends on the available flow rate (Q) and the head (H). Very briefly the greater the flow rate and the net head, the more electricity can be produced in a HPP. The first hydropower station of Turkey had been opened at Tarsus town in 1929. Number of hydropower installations and total installed capacity has increased especially after the 1960s. In 2020, the Turkish electric production values were 32.9% from HPPs, 27.2% from thermal plants working with natural gas, 21.3% from thermal plants working with coal, 8.8% fromwind power plants, 6.8% from the sun, 1.6% from geothermal plants, and about 1.4% from other types of sources. Technically and economically feasible total hydroelectric energy potential of Turkey is 180 billion kWh/year, of which 160 billion kWh/year has been developed and completed. With 714 completed facilities and 31,391 MW installed power and 108.0 billion kWh/year of it has been put into operation. With the projects to be established until 2023, a total installed power capacity of 40,000 MW and a generation potential of 135 billion kWh/year will be reached. Because of the very fast increase in energy consumption, and only 22% of total energy is produced from national sources, and 125 billion dollars total investment is needed. Due to the climate change, and the change in the oil prices, the renewable sources such as solar, wind, geothermal, biogas, biomass, hydropower etc. should be developed and put in service as quickly and efficiently as possible. In this paper, the current level of hydropower production and energy saving, and power consumption by different sectors, and the subject matter of the most recent energy figures are given and the future projections are also presented.Item The effects of coating conditions on the friction and corrosion resistance of carbon steel(2020) Guler, Ebru Saraloglu; Buyukluoglu, Berkay; 0000-0002-3732-1268; AAD-1956-2020Coatings are applied by using several methods to ensure low friction with high corrosion and wear resistance, particularly in gear applications. The friction and corrosion performance of black-phosphate-coated carbon steel at different temperatures and operating times were studied in this study. Moreover, comparison of the black phosphate coating and traditional manganese coating was conducted in terms of friction coefficient and corrosion resistance. The optimum temperature and time for black-phosphate-coated steels were 70 degrees C and 20 min, respectively. The coating temperature showed a significant effect, whereas time displayed a minor effect on friction, but both of the results favor a lower energy cost. The average friction coefficient of black-phosphate-coated sample was calculated as half of the one obtained by manganese phosphate coating under the same coating conditions.