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  • Küçük Resim
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    Case Study About Economic Order Quantities and Comparison of Results From Conventional Eoq Model and Response Surface-Based Approach
    (POLSKA AKAD NAUK, POLISH ACAD SCIENCESPL DEFILAD 1, WARSZAWA 00-901, POLAND, 2018) Yıldız, Ramazan; Yaman, Ramazan
    This study involves the implementation of an economic order quantity (EOQ) model which is an inventory control method in a ceramic factory. Two different methods were applied for the calculation of EOQs. The first method is to determine EOQ values using a response surface method-based approach (RSM). The second method uses conventional EOQ calculations. To produce a ceramic product, 281 different and additive materials may be used. First, Pareto (ABC) analysis was performed to determine which of the materials have higher priority. Because of this analysis, the value of 21 items among 281 different materials and additives were compared to the ratio of the total product. The ratio was found to be 70.4% so calculations were made for 21 items. Usage value for every single item for the years 2011, 2012, 2013 and 2014, respectively, were obtained from the company records. Eight different demand forecasting methods were applied to find the amount of the demand in EOQ. As a result of forecasting, the EOQ of the items were calculated by establishing a model. Also, EOQ and RSM calculations for the items were made and both calculation results were compared to each other. Considering the obtained results, it is understood that RSM can be used in EOQ calculations rather than the conventional EOQ model. Also, there are big differences between the EOQ values which were implemented by the company and the values calculated. Because of this work, the RSM-based EOQ approach can be used to decide on the EOQ calculations as a way of improving the system performance.
  • Küçük Resim
    Öğe
    Fırçasız DA motorunun hız kontrolünde PI katsayılarının Pareto tabanlı çok amaçlı optimizasyonu
    (Balıkesir Üniversitesi, 2018) Calgan, Haris; Yaman, Ramazan; İlten, Erdem; Demirtaş, Metin
    Bu makale PI kontrolör katsayılarının (Oransal kazanç Kp and Integral kazanç Ki) optimum değerlerini bulmak için Elman Yapay Sinir Ağları (EYSA) modeli kullanılan Pareto tabanlı çok amaçlı optimizasyonu ve Yanıt Yüzey Yöntemi’nin (YYY) karşılaştırılmasını sunmaktadır. Amaç fonksiyonu olarak oturma süresi (Ts) ve maksimum aşma (Mo) seçilmiştir. Çalışmanın amacı, PI kontrolör parametre katsayıları olan Kp ve Ki’nin optimum değerlerinin bulunmasıdır. İlk olarak, Minitab programı kullanılarak deney tasarımı gerçekleştirilmiştir. Daha sonra fırçasız doğru akım motoru hız kontrol sisteminin matematiksel modelinin oluşturulması için YYY ve EYSA modeli ayrı ayrı elde edilmiştir. Son olarak da, optimizasyon işlemi her iki yöntem ile ayrı ayrı gerçekleştirilmiştir. Optimizasyon işlemleri sonucunda, katsayıların optimum değerleri ve Pareto eğrisi elde edilmiştir. Elde edilen optimum değerler, sistemde kontrolör içerisine yazılarak fırçasız DA motorun gerçek zamanlı çıkışları elde edilmiştir. Sonuçlar karşılaştırıldığında, Pareto tabanlı EYSA yönteminde daha iyi performans sağlandığı görülmüştür.
  • Küçük Resim
    Öğe
    Validation of Computational Fluid Dynamic Analysis of Natural Convection Conditions for A Resin Dry-type Transformer with A Cabin
    (VINCA INST NUCLEAR SCI, MIHAJLA PETROVICA-ALASA 12-14 VINCA, 11037 BELGRADE. POB 522, BELGRADE, 11001, SERBIA, 2019) Yaman, Gülşen; Altay, Ramazan; Yaman, Ramazan
    Many industrial products work under different constraints. Examples of these products include transformers and keeping them in certain operating temperatures is an important design constraint. However, since power transformers have different requirements, there are no standard products. For this reason, it is difficult and costly to test each one by considering these constraints and to design them accordingly. Satisfactory thermal analysis using a 3-D finite volume-based CFD model is an important step to understand natural convection and necessary design modifications under the desired conditions. The aim of this study is to verify the performance and reliability of the design by comparing the experimental results with 3-D finite volume analysis results by considering cooling of a dry resin type transformer with a cabin. The effect of the cabin on the product in terms of natural heat convection is also evaluated.