A fuzzy based decision support system for air conditioner selection and an application to Turkish construction sector

U građevinarstvu su klima uređaji - air conditioners (AC) bitni konstrukcijski elementi od direktnog utjecaja na udobnost i zdravlje ljudi. U tom kontekstu postupak izbora odgovarajućeg uređaja zahtijeva primjenu metoda za donošenje odluke s više kriterija (MCDM - multi-criteria decision making) zbog kontradiktornih kriterija kao što su kupovni troškovi i troškovi održavanja, zadovoljavajuća tehnička svojstva, kvaliteta upotrebe, radne karakteristike itd. U radu se daju jasni, sustavni pristupi i u fuzzy i u crisp okruženju za izbor odgovarajućeg klima uređaja i predlaže model za pomoć onima u građevinskom sektoru koji donose odluku da procijene mogućnosti raznih proizvoda. Podaci potrebni za matrice donošenja odluke dobivaju se putem upitnika podijeljenih stručnjacima kao i podrobnih razgovora s ekspertima koji rade u jednoj od vodećih građevinskih tvrtki te proučavanjem podataka iz prethodnih istraživanja. Predloženi je model također primijenjen u vodećem građevinskom poduzeću u Turskoj.In the construction industry, air conditioners (AC) are vital structural segments affecting human’s comfort and health directly. In this context selection process for the proper AC requires the usage of multi-criteria decision making (MCDM) methods due to conflicting criteria such as purchasing and maintenance costs, technical sufficiency, quality of service, performance, etc. This study provides distinct systematic approaches both in fuzzy and crisp environments to deal with the selection problem of appropriate AC and proposes a decision support model helping decision makers in construction sector to assess the potentials of different products. The required data for decision matrices is obtained via a questionnaire administered to specialists as well as deep discussions with experts working in one of the leading construction firms and making use of past studies. An application of the proposed model is also performed in a leading construction company in Turkey

A flight planning model and a case study in an airline company

Havacılık endüstrisindeki gelişmeler, ülke refah seviyesini arttırmaktadır. Diğer ulaştırma modlarına kıyasla hava taşımacılığının ekonomik ve sosyal etkilerinin tahmin edilemeyecek kadar büyük olması konu üzerinde çalışmayı cazip hale getirmektedir. Bunun nedeni, maliyet, uçuş yükünün uçaklar arası düzgün dağılımı, yaşanan gecikmeler veya herhangi bir konudaki küçük iyileştirmelerin havacılık endüstrisinde büyük kazanımlara neden olmasıdır. Havacılık, ayrı ayrı veya bir arada ele alınması gereken çok sayıdaki birbiriyle ilişkili operasyonu içeren karmaşık bir endüstridir. Bir problemin çıktısı, bir diğerinin girdisidir. Bu nedenle, bir problemde başarılı olabilmek için önceki problemler dikkatlice incelenmeli ve çözülmelidir. Uçak Bakım Rotalama, Uçuş Çizelgeleme, Filo Atama, Mürettebat Çizelgeleme ve Bozulma Giderme gibi bu sektördeki önemli havayolu operasyonları arasında büyüleyici zorluklara sahip problemlerden biridir. Bu problemde, çizelgelenen uçuşlar belli bir filoda yer alan uçaklara atanır. Diğer kısıtların yanı sıra, havayolu firmaları bu süreçte uçakların bakım gereksinimlerini de karşılamalıdır. Bu, uçakların düzenli aralıklarla bakım görmesi gerektiği anlamına gelir. Unutulmamalıdır ki, fazla sayıda planlı bakım gereğinden fazla masrafa, az sayıda planlı bakım ise gereksinimlerin ihlaline neden olur. Bu tezde, birbiriyle çelişen aşağıdaki iki amacı optimize ederek en iyi rotalama seçeneklerinin belirlendiği Günlük Uçak Bakım Rotalama Problemi incelenmiştir: (1) Her bir uçuşa ait müşteri talebi ile söz konusu uçuşun atandığı uçağın kapasitesini dengelemek, (2) her bir uçağın yasal uçuş süresini mümkün olduğunca kullanmak. Bu nedenle, bakım periyodu (sadece geceleyin veya herhangi bir zamanda) göz önüne alınarak, iki farklı modelleme yaklaşımı (biri diğerinin özel bir halidir) önerilmiştir. Bu matematiksel modeller küçük ve orta ölçekli problemler için en uygun rota seçeneklerini bulabilmelerine rağmen, gerçek hayat problemleri için makul bir sürede sonuç üretememektedirler. Bu zorlukla başa çıkmak için Elitist Non-Dominated Sorting Genetic Algoritmasını (NSGA-II) temel alan bir meta-sezgisel geliştirilmiştir. Sunulan matematiksel modellerin yetersiz kaldığı durumları ve önerilen çözüm yaklaşımının etkililiğini göstermek için kapsamlı sayısal analizler yapılmıştır. -------------------- Developments in aviation industry improves the prosperity level in a country. Compared to other modes of transport, air transport’s economic and social impacts are unpredictably large which makes it an attractive subject to work on. This is because, small improvements in costs, robustness, flight load smoothness, flight delays or any issue, may cause big gains in aviation industry. Aviation is a complex industry including lots of interrelated airline operations which must be handled separately or together. Output of one problem is input of another’s. Hence, to have success in one problem, previous problems should be carefully examined and solved. Among the numerous leading airline operations in this industry such as Flight Scheduling, Fleet Assignment, Crew Scheduling and Disruption Recovery, the Aircraft Maintenance Routing is one of the fascinating challenges. In this problem, flights that must be scheduled are assigned to aircrafts within a specific fleet. Among other constraints, airlines must fulfill maintenance requirements during this routing process, which means that aircrafts must receive maintenance at regular intervals. Too much planned maintenance is costly and too little may violate requirements. In this thesis, daily Aircraft Maintenance Routing Problem is studied to determine the best routing choices that optimize the following conflicting objectives: (1) To balance each flight’s customer demand with the capacity of the aircraft to which the flight in question is assigned, (2) to use each aircraft’s legal flight time as much as possible. For this reason, considering the maintenance period (only at night or at any time), two different modelling approaches (one of which is a special case of the other) are proposed. Although, these mathematical models are capable of finding optimal routes for small and moderate scale problems, they fail to give results for real life problems in a reasonable time. Hence, a meta-heuristic approach which is based on Elitist Non-Dominated Sorting Genetic Algorithm (NSGA-II), is developed to handle this difficulty. Comprehensive numerical analyses have been carried out to show the situations where the mathematical models are insufficient and the effectiveness of the proposed approach

A fuzzy based decision support model for non-traditional machining process selection

Primjena ne-tradicionalnih procesa obrade naglo se povećava, zajedno s povećanjem potražnje i korištenja složenih materijala visoke čvrstoće, otpornih na temperaturu. Zbog svojih prednosti, kao što su brzina rezanja, kvaliteta površine i ekonomičnosti, oni su postali vitalni proces proizvodnje. Zbog sukobljenih kriterija, izbor odgovarajuće ne-tradicionalne strojne obrade uveliko zahtijeva korištenje metoda višekriterijskog odlučivanja. Ovaj rad pruža različite sustavne pristupe kako u području neizrazite tako i čvrste logike kod odabira odgovarajućeg ne-tradicionalnog postupka strojne obrade i predlaže model za podršku odlučivanju vodećih donositelja odluka u procjeni potencijala različitih ne-tradicionalnih procesa obrade. Potrebni podaci za matrice u odlučivanju dobivaju se putem upitnika za stručnjake, temeljitim raspravama sa ekspertima, korištenjem postojećih radova i eksperimentalno. Primjena predloženog modela također je izvedena kako bi se pokazala njegova primjenljivost.Usages of non-traditional machining processes are rapidly increasing together with increases in demand and usage of high strength, temperature resistant and complex materials. Due to their advantages such as cutting speed, surface quality and economizing, they became a vital process of manufacturing. Because of the conflicting criteria, the selections of appropriate non-traditional machining process highly require usage of multi criteria decision making methods. This study provides distinct systematic approaches both in fuzzy and crisp domain to deal with the selection problem of appropriate non-traditional machining process and proposes a decision support model for forth leading decision makers to assess potentials of distinct non-traditional machining processes. The required data for decision matrices is obtained via a questionnaire to specialists as well as deep discussions with experts, making use of past studies, and experimentally. An application of the proposed model is also performed to show the applicability of the model

A fuzzy based decision model for nontraditional machining process selection

Manufacturing systems are processes in which inputs obtained from interior and exterior sources are transformed into an output by gathering inputs in an optimal way to guide the enterprises. Machining process plays a critical role in industry, and thus, directly affects the efficiency of the manufacturing systems. Due to different importance of the conflicting criterions, the multi-criteria decision-making methods are extremely useful in the selection process of the proper machining type. This study provides distinct systematic approaches in fuzzy and crisp environments to deal with the selection problem of proper machining process and proposes a decision support model for the guidance of decision makers to assess potentials of seven distinct nontraditional machining processes, namely laser beam machining, plasma arc machining, water jet machining, abrasive water jet machining, electrochemical machining, electrical discharge machining (EDM), and wire–EDM in the cutting process of carbon structural steel with the width of plate of 10 mm. The required data for decision and weight matrices are obtained via a questionnaire to specialists, as well as by deep discussions with experts and making use of past studies. Finally, an application of the proposed model is also performed via the SETED 1.0 software to show the applicability of the model.Web of Science709-102282227

Verfahren zur Bestimmung der Enthalpie und Entropie für das Laserschneiden

This paper is devoted to the mechanisms of laser cutting of material from the point of view of thermodynamics. Thanks to the special properties of a laser beam, lasers have proved to be a reliable tool for the industry. Scientific databases currently include many papers devoted to scientific and engineering research aimed at the development and application of the technology of lasers. Operating costs of a laser system are high when operated inefficiently, therefore efficient operation is quite desirable. High dimensional accuracy and mainly good final product quality must be achieved in order to ensure the effective laser cutting. Investigation into thermodynamic efficiencies and quality assessment of the final product in laser cutting is essential. We have created an analytical expression of the thermo-dynamic parameters of the cut. By expression of the entropy S, enthalpy H, heat flow density q and Gibbs' function of free energy G a complex image of thermo-dynamic conditions of the process was achieved. These are the basic thermodynamic parameters of the laser cutting of materials. All these factors under operating conditions had an impact on the surface quality of the cut, depth of the cut and also on the intensity of changes in the mechanical properties of the material, and last but not least, on productivity and competitiveness. This can be used both for predictions concerning the technology process, as well as for control of the process.Dieser Beitrag ist den Mechanismen des Laserschneidens von Material aus der Sicht der Thermodynamik gewidmet. Durch die speziellen Eigenschaften eines Laserstrahls haben sich Laser als zuverlässiges Werkzeug für die Industrie etabliert. Wissenschaftliche Datenbanken umfassen derzeit viele Beiträge, die der wissenschaftlichen und technischen Forschung an der Entwicklung und Anwendung der Lasertechnologie gewidmet sind. Die Betriebskosten eines Lasersystems sind bei nicht effizienter Betriebsweise hoch, so dass ein effizienter Betrieb wünschenswert ist. Hohe Maßgenauigkeit und vor allem gute Qualität des Endprodukts sind wichtig, um die Effektivität des Laserschneidens zu gewährleisten. Wir haben einen analytischen Ausdruck der thermodynamischen Parameter des Einschnitts abgeleitet. In den Ausdrücken der Entropie S, der Enthalpie H, der Wärmestromdichte q und der Gibbs-Funktion der freien Energie G konnte ein komplexes Bild der thermodynamischen Bedingungen des Verfahrens dargestellt werden. Dies sind damit die grundlegenden thermodynamischen Parameter der Laserschneiden von Materialien. Alle diese Faktoren haben unter Betriebsbedingungen eine Auswirkung auf die Oberflächengüte des Einschnitts, die Schnitttiefe und auch auf die Intensität der Veränderungen der mechanischen Eigenschaften des Materials sowie nicht zuletzt auch auf die Produktivität und Wettbewerbsfähigkeit. Dies kann sowohl für die Vorhersagen über den Technologieprozess als auch zur Steuerung des Prozesses verwendet werden.Web of Science475-646145