Yazar "Toklu, Y. Cengiz" seçeneğine göre listele

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    Application of Big Bang - Big Crunch Optimization to Resource Constrained Scheduling Problems
    (Korean Society Of Civil Engineers-Ksce, 2018) Toklu, Y. Cengiz
    Last decades have witnessed emergence of many different solution techniques proposed for resource constrained construction scheduling problems. High majority of these solutions involve metaheuristic techniques. Almost all of the techniques involving metaheuristic techniques are based on the search of the most convenient ordering of activities. In this study, a different approach is applied, namely, the search for the most convenient vector involving the early start days of the activities. This choice necessitated creation of two special operators called left-compression operator and right-compression operator. The use of these operators enabled determination of critical activities and critical paths for the problems with resource constraints. Analyses on example problems have indicated that for a given problem the optimum solution may not be unique, and on the other hand, there may be sub-optimal solutions where all activities are critical. The metaheuristic method used in the study is the Big Bang - Big Crunch Optimization, which could not have been applied to this problem if the vector of unknowns were considered as the ordered set of activities.
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    Production of a set of lunar regolith simulants based on Apollo and Chinese samples
    (Elsevier Sci Ltd, 2023) Toklu, Y. Cengiz; Acikbas, Nurcan Calis; Acikbas, Gokhan; Cercevik, Ali Erdem; Akpinar, Pinar
    Designing lunar shelters with appropriate construction techniques and in-situ materials is a novel and exciting field where many researchers from different countries are working. The first step in working in this field is producing lunar soil simulants on earth that will serve for improving lunar construction materials, as lunar soils are the only in-situ resources available for lunar constructions. Up to date, 9 countries have produced lunar soil simulants and the last contribution has been made by Tu & BULL;rkiye as expressed in this study. The technique, of which the properties are explained in this publication, enables the determination of simulant to any lunar soil. When the lunar construction materials are of main concern, the mineral and chemical composition of the lunar soils and the simulants are more critical than their certain geotechnical characteristics since the chemical interactions within the material will primarily define the con-struction material's performance. Hence, as an important preliminary step in accurate lunar soil simulant production, this study focuses on the determination and matching of the targeted chemical compositions for lunar soil simulants. For this reason, mineralogical analysis of the samples with XRD and chemical compositions with XRF analysis were determined. A novel method was applied during the deter-mination of the simulant, which kept all lunar soil samples with known characteristics as possible targets instead of employing only one targeted soil sample. This enabled the determination of the mentioned new simulant with best fit to a previously known lunar soil sample, while using an attainable budget. The procedure also enabled producing a simulant to a newcomer, the CE-5 Chinese lunar soil, in a very short time.& COPY; 2023 COSPAR. Published by Elsevier B.V. All rights reserved.
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    Turkish Lunar Regolith Simulant TBG-1
    (Amer Soc Civil Engineers, 2023) Toklu, Y. Cengiz; Acikbas, Nurcan Calis; Acikbas, Gokhan; Cercevik, Ali Erdem; Akpinar, Pinar
    Being terrestrial for so many thousands of years, humanity is now advancing in the direction of being extraterrestrial. Attempts made until now were quite promising, like walking on the Moon, living in stations for very long durations miles away from Earth, sending probes to unimaginable distances in space and bringing them back to Earth, etc. In the coming decades, it is easily predictable that man will spend time on Moon in lunar shelters for periods which cannot be qualified as short visits. This will be followed by going to Mars and other space bodies. Such achievements will be realized thanks to space research conducted in space agencies all around world, especially by countries who can afford huge amounts of money in this field. In fact, space research is a multi-dimensional, multi-disciplinary field where important contributions can be made without having much financial support. Such an approach, evidently, will increase international cooperation in the field, and will help increasing technological and scientific levels of all countries who join this research subject. Designing shelters specially adopted to lunar environmental conditions and finding ways of construction techniques for building them is but a field where many researchers from many countries can attack. A related field is producing lunar soil simulants on Earth and making experiments on them for using lunar soil as the only in situ resource available in construction and for extracting other compounds and elements that will be needed for human survival on Moon. It is to be noted that up to date 9 countries have produced lunar soil simulants and this number is increasing continuously. The last contribution is from Turkey, with the lunar soil simulant labeled TBG-1 about which general information and properties are given in this study.