Meslek Yüksekokulları

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Criticality Investigations for the Fixed Bed Nuclear Reactor Using Thorium Fuel Mixed with Plutonium or Minor Actinides
(Pergamon-Elsevier Science Ltd, 2009) Sahin, Suemer; Sahin, Haci Mehmet; Acir, Adem; Al-Kusayer, Tawfik Ahmed
Prospective fuels for a new reactor type, the so called fixed bed nuclear reactor (FBNR) are investigated with respect to reactor criticality. These are (1) low enriched uranium (LEU); (2) weapon grade plutonium + ThO2; (3) reactor grade plutonium + ThO2; and (4) minor actinides in the spent fuel of light water reactors (LWRs) + ThO2. Reactor grade plutonium and minor actinides are considered as highly radioactive and radio-toxic nuclear waste products so that one can expect that they will have negative fuel costs. The criticality calculations are conducted with SCALE5.1 using S-8-P-3 approximation in 238 neutron energy groups with 90 groups in thermal energy region. The study has shown that the reactor criticality has lower values with uranium fuel and increases passing to minor actinides, reactor grade plutonium and weapon grade plutonium. Using LEU, an enrichment grade of 9% has resulted with k(eff) = 1.2744. Mixed fuel with weapon grade plutonium made of 20% PuO2 + 80% ThO2 yields k(eff) = 1.2864. Whereas a mixed fuel with reactor grade plutonium made of 35% PuO2 + 65% ThO2 brings it to k(eff) = 1.267. Even the very hazardous nuclear waste of LWRs, namely minor actinides turn out to be high quality nuclear fuel due to the excellent neutron economy of FBNR. A relatively high reactor criticality of k(eff) = 1.2673 is achieved by 50% MAO(2) + 50% ThO2. The hazardous actinide nuclear waste products can be transmuted and utilized as fuel in situ. A further output of the study is the possibility of using thorium as breeding material in combination with these new alternative fuels. (C) 2009 Elsevier Ltd. All rights reserved.
Fuzzy Modelling of Static System Optimum Traffic Assignment Problem Having Multi Origin-Destination Pair
(Elsevier Science Inc, 2021) Temelcan, Gizem; Kocken, Hale Gonce; Albayrak, Inci
Traffic congestion is an unpreventable problem to avoid in a transportation network and it has negative effects on traffic accident, time wasting, traffic delay and safety problem. Besides, in transportation networks, drivers do not want to deal with traffic jam while traversing between specified origin-destination pair. Therefore, traffic assignment (TA) is imperative to improve traffic management, transportation safety, time, and cost savings. System Optimum Traffic Assignment Problem (SOTAP) is a kind of TA model which aims to minimize the total system travel time on the network, and satisfies the flow conservation constraints. To model the SOTAP more realistically, the imprecise parameters can be taken as fuzzy. Therefore, in this paper, we focus on converting the conventional SOTAP to a fuzzy quadratic programming problem (QPP) which is named System Optimum Fuzzy Traffic Assignment Problem (SOFTAP). Here, link travel time is expressed with BPR function as generally used in the literature by converting to fuzzy except link-dependent parameters. Thus, the nonlinear objective function of SOFTAP is expressed in terms of fuzzy link flows and fuzzy link travel times. A solution approach from the literature is modified to the reconstructed SOFTAP.
A New Simulation Modelling Approach to Continuous Berth Allocation
(Taylor & Francis Ltd, 2013) Esmer, Soner; Yildiz, Gokalp; Tuna, Okan
Within the international supply chain and logistics system, ports are an important ring of the basic transport activities. Thus, any shortage in or lack of well-planned orders encountered in the port operation processes is most likely to affect the whole logistic system, which eventually will cause undesirable delays in deliveries. This study aims at developing a simulation modelling approach to continuous berth allocation in Port of Izmir Alsancak, which has continuous quayside with two main wharfs perpendicular to each other. The simulation models which serve to evaluate the proposed modelling approach have been developed in ARENA 10.0 Simulation Software. The results of the conducted computational experiments showed that the proposed modelling approach provides more accurate and realistic estimates of performance measures, such as average berth utilisation, average ship waiting time in a queue, and the average number of ships in queuing up to get container terminals.
The Political Economy of Housing Financialization in Turkey: Links with and Contradictions to the Accumulation Model
(Routledge Journals, Taylor & Francis Ltd, 2020) Erguven, Emre
Financialization influenced the Turkish economy and housing industry mostly through financial liberalization moves and soaring capital inflows. It both increased household liabilities and mortgage loans dramatically and offered various facilities for the housing industry. Relevant legal regulations not only helped the Turkish housing industry prosper but also eased its integration into the national and global financial system. In addition, political implications constituted a strong motivation for governments to attach special importance to the housing industry. I examine housing financialization as an integral part of the accumulation model of the Turkish economy and argue that the housing industry lies at the very heart of the contradictions of this model. The large-scale capital inflows both intensified the dependency on foreign resources and increased the role of the domestic demand. This is the main contradiction of the accumulation model; it manifests itself in the interest rate dilemma and is also critical for housing financialization in Turkey because the characteristics of this model are especially valid for the housing industry. Moreover, not only do the contradictions of the accumulation model disrupt the housing industry, but also the characteristics of the housing industry contribute to the disruption of this model.
The Prioritisation of Service Dimensions in Logistics Centres: A Fuzzy Quality Function Deployment Methodology
(Taylor & Francis Ltd, 2016) Vural, Ceren Altuntas; Tuna, Okan
This study takes a customer focus that prioritises the service-offering dimensions of logistics centres (LCs) by considering potential LC customer expectations. Applying a survey and a quality function deployment methodology to logistics service providers, the study explores, categorises and prioritises LC customer expectations and LC service characteristics. The results indicate that customer preferences mainly prioritise infrastructure, and warehouse and intermodal dimensions. However, when the cost dimension is included, higher utility values are delivered through soft service dimensions like value-added or standard services. LC investors or undertakers can use these results to guide their design of market offerings by using the same methodology to assess expectations in their target markets.

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