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Summary This review underlines the importance of the developments in perovskite catalysts for methane combustion from the past up to the present. In this review, after a general and brief introduction to perovskites, the mechanisms of catalytic combustion of methane have been included. Moreover, current studies on perovskites have been summarized including the effects of substitutions, doped perovskites, perovskite preparation methods, and the effect of sulfur presence on perovskite catalysts. Besides, recent studies on perovskite oxides and phenomenon of oxygen (O2) deficiency, porous perovskite oxides, and nanostructured perovskites have been conducted. In addition, partial oxidation of methane (POM) has been reviewed. The loss of active component during the POM reaction can take place in the nickel catalyst, in particular. Since nickel has a lower melting point than noble metals and other active components, such as Co and Fe, in general, to deactivate nickel is easier. Compared with conventional structure, the porous structure with the unique morphology significantly enhances the catalytic activity through a much larger surface area (SA) and greater reactivity of the active sites. Furthermore, the monolithic nanoarrayed perovskite presents very good results in well‐defined faceted catalysts and takes part in porous channel hydrocarbon combustion. This review study is prepared as a guide to cover the profound knowledge of perovskite oxides catalysts, considering the methane combustion reaction mechanisms, and addresses prospective studies in this field for researchers.

Application of fuzzy DEMATEL technique to assess most common critical operational faults of marine boilers Gemi kazanlarının en yaygın kritik operasyonel arızalarının bulanık DEMATEL tekniğiyle değerlendirilme uygulamasıYazar(lar) (Author(s)): Veysi BAŞHAN 1 , Hakan DEMİREL 2 ORCID 1 : 0000-0002-1070-1754 ORCID 2 : 0000-0002-7579-7064 Bu makaleye şu şekilde atıfta bulunabilirsiniz(To cite to this article): Başhan V. and Demirel H. "application of fuzzy Dematel technique to assess most common critical operational faults of marine boilers", Politeknik Dergisi, *(*): *, (*). ABSTRACTWhether it is steam powered or has an internal combustion engine as the main engine of propulsion, a ship without a boiler is unimaginable; somehow a boiler, which is indispensable on ships is needed. Boiler, one of the most important ship auxiliary engines, is used for several purposes that consist of heating of fuel tanks, machinery equipment and accommodation. Many problems can arise in boilers which are designed to work with main engine exhaust gas so that the waste heat can be used in order to match expectations of energy efficiency requirements. When ship systems are analyzed, it is understood that many systems are related to each other. If there is a problem with the boiler many systems will be affected and many problems will be encountered. Therefore, this study provides a fuzzy DEMATEL (Decision Making Trial and Evaluation Laboratory) method to assess most common critical operational faults in marine boilers. The DEMATEL method gives chances to identify and analyses the important faults of marine boiler with respect to cause effect relationship diagram. Likewise, fuzzy sets get through with the uncertainty in decision making and experts comments on DEMATEL. When the results are examined, it is understood that "boiler takes excessive time to reach pressure" is important in terms of the reasons. When the effects are examined, it is seen that the most important effect is "leakage from pipes or valves". The acquired results of the research will contribute to ship boilers operational safety and prevention of dangerous machinery effects. Keywords: Marine boiler, fuzzy DEMATEL, faults, safety. Gemi Kazanlarının En Yaygın Kritik OperasyonelArızalarının Bulanık DEMATEL Tekniğiyle Değerlendirilme Uygulaması ÖZTahrik sisteminin ana motoru olarak ister buharla çalışan isterse de içten yanmalı motora sahip olan bir geminin, kazansız olması hayal edilemezdir; her şekilde, gemilerde vazgeçilmez bir yardımcı makine olan kazana ihtiyaç vardır. En önemli gemi yardımcı makinelerinden biri olan kazan; yakıt tanklarının, makine ekipmanlarının ve yaşam mahallinin ısıtılmasını içeren çeşitli amaçlarla kullanılmaktadır. Gemi ana makinesi egzoz gazı ile çalışacak şekilde tasarlanmakta ve bu sayede atık ısı, enerji verimliliği gereksinimlerinin beklentilerini karşılayacak şekilde kullanılabilmektedir. Bu sistemlerde kazanlarda birçok sorun ortaya çıkabilir. Gemi sistemleri incelendiğinde, birçok sistemin birbiriyle ilişkili olduğu anlaşılmaktadır...

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It is known that trade by ship is a cheaper way than airway, land, and rail trade. One of the most important reasons for this is that ships use heavy fuel oil (HFO), which is cheap but also poor quality fuel. This HFO used in ships needs to be cleaned with machines called separators (purifiers). Therefore, the separator is one of the vital auxiliary machines on the ship. A satisfactory separation should be done in order to get rid of the effects such as water in the fuel, sludge formation, pump ability, mixing of different grades in the tanks, abrasion, and corrosion, which are the most important risks in the burning of fuel oil. Many problems are encountered while trying to make good separation. Therefore, in this article, 20 important problems that are frequently encountered in ship HFO separators are evaluated with the best-worst method (BWM) by consulting marine experts. Results show that dirty separator discs (also fractured or broken), wrong gravity disc choice (or bad interface position), and unsatisfactory bowl work are the most important problems among 20 critical and frequent separator problems. Problems and results are very important in terms of smooth ship machinery operations and we think that this study will close this gap in the literature by ordering and identifying problems and also solution recommendations.