Akademik Arşiv / Academic Archive

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Start date: 2020

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Now showing 1 - 10 of 648
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    Development of a Restraint System for Rear-Facing Car Seats
    (Machines, 2023-01-01) Himmetoğlu, Selçuk; Yavuz, Samet
    In self-driving vehicles, passengers can set their seats in an unconventional seating position, such as rear-facing. Sitting in such an orientation can increase the risk of whiplash in the head-and-neck system in a frontal impact, as frontal crashes usually have higher severities compared with rear-end crashes. This paper shows that a forward-facing front seat optimised for rear-impact protection needs to be redesigned to be used as a rear-facing seat. In the second and main part of this paper, a restraint system for rear-facing car seats is developed, and frontal impact simulations with 64 km/h of delta-V are used to evaluate its performance. The designed seating system comprises two rigid torso plates, a fixed recliner and an energy absorber under the seat pan. Without using the developed restraint system, the 50th percentile male human model is exposed to neck shear forces exceeding 600 N. With the developed restraint system, neck shear forces are less than 350 N in frontal impacts with 64 km/h of delta-V. Apart from whiplash, the risk of head, chest, lower extremity and lower back injuries are also evaluated. The results confirm that the developed restraint system successfully protects the occupant since all assessment criteria values are lower than the injury assessment reference values.
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    Latest Optimization Approaches for Biogas Supply Chain Management A Literature Survey
    (2021-01-01) S. Erol; Güner, Gürkan Güven
    The efficient use of renewable energy sources is very critical because of the economic reasons. Considering the extreme usage of the fossil fuels around the world, it is also very critical in terms of protecting nature and human health. The use of biogas, which is one of the significant renewable energy sources, is very common in many countries because of its wide usage areas. For example, the recovered biogas can be used for electricity, heating, and transportation fuel. The greenhouse gas (GHG) emission, which causes global climate change, can be reduced significantly by the use of biogas. The optimization of biogas supply chain is necessary to ensure the demand of biogas and biofertilizer by maximum profit and minimum environmental damage. Determining the optimal location of production and purification technologies for the biogas by considering the installation requirements is important to minimize the cost. There are many studies in the literature that try to find alternative solutions by developing different methodological approaches for the optimization of biogas supply chain. In this study, latest studies in the literature are investigated, classified and compared. It is aimed that the implemented literature survey in this study becomes a beneficial guide to develop alternative solution approaches.
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    A Multi-Criteria Solution Approach for the Alternative Preventive Maintenance Applications in the Aviation Industry
    (2022-01-01) B. Gever Ekinci; Güner, Gürkan Güven; C. Balıkçı
    For the aircrafts to continue their operations actively, implementing systematic maintenance to the aircrafts are required by the aircraft manufacturers and civil aviation authorities. These operations are carried out by the aircraft operating companies as a priority. How often and at what levels the maintenance will be applied is specified in the maintenance manual published by the manufacturers. The maintenance to be performed varies depending on the mission feature of the aircraft, the flight time, or a certain calendar period. The aviation administration periodically classifies the maintenance concepts to be applied according to the frequency of maintenance by taking advantage of the maintenance criteria determined in the maintenance manual. In this classification, the maintenance operations are arranged based on "preventive maintenance" for the aircrafts to continue their activities effectively. The applied maintenance concepts are determined in the military and civilian sectors in accordance with the intended use of aircraft. In this study, in terms of the criteria determined by the application of Multi-Criteria Decision-Making methods in the literature, the most critical aircraft parts for the alternative preventive maintenance applications were identified with the real data of the Cessna 172 Skyhawk training aircrafts. After determining the criterion weights with AHP (Analytical Hierarchy Process) method, the most critical aircraft parts were prioritized with the AHPweighted TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) method. The criteria considered in the study are the unit cost, the lead time, and the total number of failures in a year of the aircraft part. Then, the reliability analyses are performed to suggest an alternative age-based preventive maintenance policy. In accordance with this purpose, real failure data are analyzed to find failure probability distributions, mean times between replacements, and cost efficiency values of each critical part. As a result, an alternative preventive maintenance policy is suggested for each critical aircraft part by determining the optimal maintenance intervals where the preventive maintenance is cost-effective. The proposed study is intended to provide guidance for alternative preventive maintenance practices in the airline industry.
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    Latest Heuristic Solution Approaches for the Analog Circuit Design Optimization A Literature Review
    (2022-01-01) Güner, Gürkan Güven; G. Demirci; B. Altunoğlu
    There are many studies, which propose different heuristic and metaheuristic solution approaches for analog circuit design optimization, in the literature. Analog circuits have great design complexity in terms of circuit parameters, and each of the analog circuit designs has different limitations because of the various requirements. In general, analog circuit design steps are composed of choosing circuit structure, then optimizing the circuit parameters. Circuit parameters need to be designed for the output of the circuit such as power, noise, and gain. Due to the complexity and time-consuming factors for the circuit design, innovative and scientific solution approaches become important for the analog circuit design solution. This study focuses on the latest heuristic and metaheuristic solution approaches, such as the evolutionary algorithms including genetic algorithm and particle swarm optimization, for the analog circuit design considering different single-objective and multi-objective problems to show the future trends about the solution methodologies. The latest studies in the literature are classified according to their purposes, solution methodologies, and considered problems. It is intended that the comprehensive literature review in this study will be helpful for the decision-makers about suggesting a course of action for the latest trends in the optimal design of the analog circuits.