Endüstri Mühendisliği Bölümü Yayın Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/279

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A Procurement Auctions-Based Framework for Coordinating Platforms in Humanitarian Logistics
(2013) Ertem, Mustafa Alp; Buyurgan, Nebil; 52460; 06.04. Endüstri Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
This chapter focuses on an auction-based procurement framework for single coordinating platforms in humanitarian logistics. It first covers disaster relief operations, humanitarian logistics, and procurement in this context and illustrate many of the issues that make the management and coordination of procurement functions complex and challenging. Then the proposed framework along with the auction model is discussed including the unique design characteristics associated with disaster relief environment. Three-phase approach presents a complete representation of the procurement in humanitarian logistics. Results indicate that the proposed announcement options increase the fill rate. Announcement construction criteria allow coordinating platforms to use varying bundling choices.
A Sociocultural Landmark in Ankara: 96lar Residential Block
(2012) Ürey Uysal, Zeynep Çiğdem; 05.02. Mimarlık; 05. Mimarlık Fakültesi; 01. Çankaya Üniversitesi
Bu çalışma, Ankaranın önemli bir kentsel simgesi olan 96lar Apartmanını, gelişiminin sosyokültürel önemi bağlamında incelemeyi amaçlamaktadır. Araştırmaların da işaret ettiği gibi 96lar Apartmanı, Ankarada 1950li ve 1980li yıllar arasında etkin olan konut gelişimi ve kooperatifçilik süreçlerinin etkisinde gelişen kendine özgü mimari planlama anlayışı ve yapım süreci dolayısıyla Ankara konut mimarisi bağlamında önemli bir yere sahip olmuştur. 96lar Apartmanının sosyokültürel gelişimini ve mimari oluşumunu döneminin kültürel, sosyal ve mimari gelişmeleri ışığında analiz etmeyi amaçlayan bu çalışma, sırasıyla Ankaradaki 1950li ve 1980li yıllar arasındaki konut üretiminden, 96lar Apartmanının bu bağlam içerisindeki yerinden, planlama anlayışı ve mimari özelliklerinden ve Modern Mimariye yaptığı referanslardan bahsedecektir.
Citation - WoS: 203
Citation - Scopus: 231
Ammonia Removal From Anaerobically Digested Dairy Manure by Struvite Precipitation
(Elsevier Sci Ltd, 2005) Uludag-Demirer, S; Demirer, GN; Chen, S; 01. Çankaya Üniversitesi; 06. Mühendislik Fakültesi; 06.04. Endüstri Mühendisliği
Ammonia is one of the most important contaminants impairing the quality of water resources. When this is considered along with the fact that the global demand for nitrogenous fertilizers is in constant rise, the need for recovery as well as removal of nitrogen is well justified. Crystallization of N and P in the form of struvite (MgNH4PO4 center dot 6H(2)O), which is a slow releasing and valuable fertilizer, is one possible technique for this purpose. This study investigated the removal of NR4+ through struvite precipitation from the effluents of one- (R1) and two-phase (R2) anaerobic reactors digesting dairy manure. To force the formation of struvite in the anaerobic reactor effluents, Ma(2+) ion was added by using both Mg(OH)(2) and MgCl2 center dot 6H(2)O. To prevent the effect of different total phosphorus (TP) concentration in the effluents of RI and R2, as well as to not limit the formation of struvite, an excess amount Of PO43- (0.14 M) was added in the form of NaHPO4. Different stoichiometric Mg2+:NH4+:PO43- ratios were tested to determine the required Mg2+ concentrations for maximum NH4+ removal by keeping NH4+:PO43- ratio constant for the effluents of reactors RI and R2. The results revealed that very high NH4+ removal efficiencies (above 95%) were possible by adding Mg 21 ions higher than 0.06 M concentration in the effluents from reactors RI and R2. It was also observed that the initial pH adjustment to 8.50 using NaOH did not result in any significant increase in the removal of NH4+ and the removal of NH4+ in the reactors treated with MgCl2 center dot 6H(2)O was higher than those treated with Mg(OH)(2) for the same Mg2+ concentration. (c) 2005 Published by Elsevier Ltd.
An approach for extending PROMETHEE to reflect choice behaviour of the decision maker
(2019) Karasakal, Esra; Karasakal, Orhan; Bozkurt, Ahmet; 216553; 06.04. Endüstri Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
In this study, an approach based on PROMETHEE is developed to correctly reflect the choice behavior of the decision maker that is not explained by the utility theory. The prospect theory argues that losses have higher impact than gains. We integrate the prospect theory into PROMETHEE through defining new preference functions. The proposed approach is behaviorally realistic and tolerates some degree of intransitivities in the preferences of the decision maker. For determining the criteria weights, we utilize pairwise comparison method of Analytic Hierarchy Process. Performance of the approach is demonstrated on a university ranking problem.
An approach to discrete convexity and its use in an optimal fleet mix problem
(Springer-Verlag Berlin, 2006) Cambini, Riccardo; Riccardi, Rossana; Yüceer, Ümit; 06.04. Endüstri Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
A notion of convexity for discrete functions is first introduced, with the aim to guarantee both the increasing monotonicity of marginal increments and the convexity of the sum of convex functions. Global optimality of local minima is then studied both for single variable functions and for multi variables ones. Finally, a concrete optimal fleet mix problem is studied, pointing out its discrete convexity properties.
An optimization model for worker assignment of a mixed model vehicle production assembly line under worker mobility
(2011) Karabak, Funda; Güner, Nizamettin Doğan; Satır, Benhür; Kandiller, Levent; Gürsoy, I.; 54700; 17931; 06.04. Endüstri Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
In this study, we consider the problem of worker assignment in a mixed model vehicle production assembly line. In particular, we focus on large size vehicles like busses and trucks that have multi zones in which workers can perform their assigned tasks simultaneously. This situation requires balancing the workloads of workers assigned in a certain set of workstations. Over the assembly line, it is allowed that workers may change their workstations during the same cycle. Moreover, each worker has a certain skill level which configures the possible set of tasks to be undertaken. Scale of the product, worker mobility and skill differences make the studied problem complicated. We propose a worker assignment model and develop a heuristic algorithm whose performance is to be evaluated against the optimal seeking methods in terms of small sized problems. We report on the validation of our heuristic algorithm in real …
Citation - WoS: 97
Citation - Scopus: 116
Anaerobic Digestion of Dairy Manure With Enhanced Ammonia Removal
(Academic Press Ltd- Elsevier Science Ltd, 2008) Uludag-Demirer, S.; Demirer, G. N.; Frear, C.; Chen, S.; 45685; 01. Çankaya Üniversitesi; 06. Mühendislik Fakültesi; 06.04. Endüstri Mühendisliği
Poor ammonia-nitrogen removal in methanogenic anaerobic reactors digesting animal manure has been reported as an important disadvantage of anaerobic digestion (AD) in several studies. Development of anaerobic processes that are capable of producing reduced ammonia-nitrogen levels in their effluent is one of the areas where further research must be pursued if AD technology is to be made more effective and economically advantageous. One approach to removing ammonia from anaerobically digested effluents is the forced precipitation of magnesium ammonium phosphate hexahydrate (MgNH4PO4-6H(2)O), commonly called struvite. Struvite is a valuable plant nutrient source for nitrogen and phosphorus since it releases them slowly and has non-burning features because of its low solubility in water. This study investigated coupling AD and controlled struvite precipitation in the same reactor to minimize the nitrogen removal costs and possibly increase the performance of the AD by reducing the ammonia concentration which has an adverse effect oil anaerobic bacteria. The results indicated that Lip to 19% extra COD and almost 11% extra NH3 removals were achieved relative to a control by adding 1750 mg/L of MgCl2-6H(2)O to the anaerobic reactor. (C) 2007 Elsevier Ltd. All rights reserved.
Citation - Scopus: 18
Analysis of Barriers To the Adoption of Circular Supply Chain Management: a Case Study in the Air Conditioning Industry
(Taylor and Francis Ltd., 2023) Çıkmak, S.; Kesici, B.; 01. Çankaya Üniversitesi
Circular supply chain management (CSCM) is a process used to design the supply chain by recycling, remanufacturing or refurbishing, repairing, and reusing products However, no study has been encountered in the literature that analyzes CSCM barriers in the air conditioning sector. Hence, this study is aimed to investigate the barriers to CSCM adoption in the air conditioning industry. A case study was conducted on a company operating in the global air conditioning sector. Initially, literature review and expert opinions have been used to identify essential barriers. Later, 6 main barriers and 21 sub-barriers were ranked using Analytical Hierarchy Process (AHP) method based on the interval type-2 fuzzy sets. The findings indicate that “Regulatory” is the most crucial, and “Operational” is the least important main barrier. The findings of the study would be useful for practitioners and policymakers to focus on the most prominent barriers in the air conditioning supply chains. © 2023 Chinese Institute of Industrial Engineers.
Citation - WoS: 12
Analysis of Dengue Transmission Dynamic Model by Stability and Hopf Bifurcation With Two-Time Delays
(Imr Press, 2023) Ambalarajan, Venkatesh; Sivakumar, Vinoth; Dhandapani, Prasantha Bharathi; Baleanu, Dumitru; Murugadoss, Prakash Raj; 56389; 02.02. Matematik; 02. Fen-Edebiyat Fakültesi; 01. Çankaya Üniversitesi
Background: Mathematical models reflecting the epidemiological dynamics of dengue infection have been discovered dating back to 1970. The four serotypes (DENV-1 to DENV-4) that cause dengue fever are antigenically related but different viruses that are transmitted by mosquitoes. It is a significant global public health issue since 2.5 billion individuals are at risk of contracting the virus. Methods: The purpose of this study is to carefully examine the transmission of dengue with a time delay. A dengue transmission dynamic model with two delays, the standard incidence, loss of immunity, recovery from infectiousness, and partial protection of the human population was developed. Results: Both endemic equilibrium and illness-free equilibrium were examined in terms of the stability theory of delay differential equations. As long as the basic reproduction number (R0) is less than unity, the illness-free equilibrium is locally asymptotically stable; however, when R0 exceeds unity, the equilibrium becomes unstable. The existence of Hopf bifurcation with delay as a bifurcation parameter and the conditions for endemic equilibrium stability were examined. To validate the theoretical results, numerical simulations were done. Conclusions: The length of the time delay in the dengue transmission epidemic model has no effect on the stability of the illness-free equilibrium. Regardless, Hopf bifurcation may occur depending on how much the delay impacts the stability of the underlying equilibrium. This mathematical modelling is effective for providing qualitative evaluations for the recovery of a huge population of afflicted community members with a time delay.
Citation - WoS: 9
Citation - Scopus: 10
Analysis of Exergy and Energy of Sugar Production Process in Sugar Plant
(Maney Publishing, 2010) Acir, A.; Altunok, T.; Baysal, E.; Kocyigit, E.; Sahin, H. M.; 40424; 01. Çankaya Üniversitesi; 06. Mühendislik Fakültesi; 06.06. Makine Mühendisliği
In this paper, the energy and exergy analysis results of sugar production processes were presented by using operational system data from the Kayseri sugar plant, Turkey. All sugar production processes were thought as a steady state open thermodynamics system and employed the energy and exergy analyses, based on the first and second laws of thermodynamics. The best values of the energy and exergy efficiencies were obtained as 95.1% for the juice production process and 74.3% for the juice concentration process respectively. Moreover, the location of the energy degradation and the irreversibility were determined during the whole sugar production processes. Consequently, it has been pointed out that the energy and exergy efficiencies can be improved if the rates of the energy degradation and irreversibility in the sugar production processes are reduced.
Citation - WoS: 26
Citation - Scopus: 36
Anti-Ship Missile Defense for a Naval Task Group
(Wiley-blackwell, 2011) Kandiller, Levent; Karasakal, Orhan; Ozdemirel, Nur Evin; 2634; 5706; 06.04. Endüstri Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
In this study, we present a new formulation for the air defense problem of warships in a naval task group and propose a solution method. We define the missile allocation problem (MAP) as the optimal allocation of a set of surface-to-air missiles (SAMs) of a naval task group to a set of attacking air targets. MAP is a new treatment of an emerging problem fostered by the rapid increase in the capabilities of anti-ship missiles (ASMs), the different levels of air defense capabilities of the warships against the ASM threat, and new technology that enables a fully coordinated and collective defense. In addition to allocating SAMs to ASMs, MAP also schedules launching of SAM rounds according to shoot-look-shoot engagement policy or its variations, considering multiple SAM systems and ASM types. MAP can be used for air defense planning under a given scenario. As thorough scenario analysis would require repetitive use of MAP, we propose efficient heuristic procedures for solving the problem. (C) 2011 Wiley Periodicals, Inc. Naval Research Logistics 58: 305-322, 2011
Citation - WoS: 6
Citation - Scopus: 7
An Approximation for Kanban Controlled Assembly Systems
(Springer, 2011) Avsar, Zeynep Muge; Topan, Engin; 164129; 06.04. Endüstri Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
An approximation is proposed to evaluate the steady-state performance of kanban controlled two-stage assembly systems. The development of the approximation is as follows. The considered continuous-time Markov chain is aggregated keeping the model exact, and this aggregate model is approximated replacing some state-dependent transition rates with constant rates. The approximate aggregate model is, then, decomposed into submodels and a product-form steady-state distribution is obtained for each submodel. Finally, the submodels are combined in such a way that the size of the problem becomes independent of the number of kanbans. This leads to the computational advantage in solving the combined model using numerical matrix-geometric solution algorithms. Numerical comparisons of the combined model with simulation, exact model, approximate aggregate model and an approximation in the literature show that the proposed approximation performs well in terms of accuracy and computational burden.
Citation - WoS: 30
Citation - Scopus: 33
An Auction-Based Framework for Resource Allocation in Disaster Relief
(Emerald Group Publishing Ltd, 2011) Buyurgan, Nebil; Ertem, Mustafa Alp; 52460; 06.04. Endüstri Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
Purpose - The purpose of this paper is to address the inefficiency problems in procurement operations in disaster relief logistics which are mainly due to the lack of coordination among less organized suppliers and partnerships. Such problems lead to poor responsiveness and hinder timely procurement of required goods. Design/methodology/approach - An auction-based framework for procurement of goods, which is suitable for a single coordinating platform in disaster relief logistics, is proposed. Integer programming formulations are used in auctioning operations. A simulation model that generates problem instances is used to evaluate and tune system-level design parameters. Findings - Design parameters greatly affect the behaviour and responsiveness of the system and the performance of the auction-based framework in different problem instances. Combinations of those parameters may allow suppliers with limited capacities to become more involved in the bidding process. In addition, the procurement shares of bidders may change substantially with different values of the parameters. Research limitations/implications - Even though the presented framework is inspired from reallife applications, it is not implemented in real-life disaster relief operations. The goodness of fit for the framework would best be evaluated by a real disaster case. In addition, transportation scheduling and vehicle routing considerations and budgeting issues are not considered in the framework. Originality/value - This paper presents an auction-based framework for less organized suppliers of goods and their partnerships, such as local humanitarian organizations, private companies, and standby partners. The presented framework offers a background for coordination during disaster relief operations which provides opportunities to act as a set of organized entities. This background also helps those entities coordinate their efforts to enhance the capabilities of local governments and NGOs.
Autoregressive Models With Stochastic Design Variables and Nonnormal İnnovations
(2011) Türker Bayrak, Özlem; Dener Akkaya, Ayşen; 56416; 2337; 09.01. Ortak Dersler Bölümü; 09. Rektörlük; 01. Çankaya Üniversitesi
In autoregression models the design variable has traditionally been assumed to be non-stochastic and innovations are normal. In most real life situations, however, the design variable is stochastic having a non-normal distribution as the innovations. Modified maximum likelihood method is utilized to estimate unknown parameters in such situations. Closed form estimators are obtained and shown to be efficient and robust.
Basit Doğrusal Otoregresif Modeller Sisteminde Parametre Tahmini ve Hipotez Testi: Simetrik İnovasyonlar
(2005) Türker, Özlem; Akkaya, Ayşen D.; 56416; 09.01. Ortak Dersler Bölümü; 09. Rektörlük; 01. Çankaya Üniversitesi
Bu çalışmada, simetrik dağılıma sahip hata terimli basit otoregresif modeller sistemi incelenerek normal dağılım varsayımının geçersiz olduğu durumlardaki metodoloji birden fazla bağımsız bilgi kaynağı olduğu durumlara genellenmiş, uyarlanmış en çok olabilirlik yöntemi ile tahmin ediciler elde edilmiş ve parametre vektörünün tüm kaynaklar için değişip değişmediğini test edecek sağlam ve etkin test istatistikleri geliştirilmiştir. Elde edilen tahmin ediciler ve test istatistikleri bu alandaki uygulamalarda sıkça kullanılan en küçük kareler yöntemi ile elde edilen tahmin edici ve test istatistikleri ile karşılaştırılmış ve daha iyi sonuçlar verdiği görülmüştür.
Citation - WoS: 23
Citation - Scopus: 26
Bi-Objective Adaptive Large Neighborhood Search Algorithm for the Healthcare Waste Periodic Location Inventory Routing Problem
(Springer Heidelberg, 2022) Aydemir-Karadag, Ayyuce; 116059; 01. Çankaya Üniversitesi
There has been an unexpected increase in the amount of healthcare waste during the COVID-19 pandemic. Managing healthcare waste is vital, as improper practices in the waste system can lead to the further spread of the virus. To develop effective and sustainable waste management systems, decisions in all processes from the source of the waste to its disposal should be evaluated together. Strategic decisions involve locating waste processing centers, while operational decisions deal with waste collection. Although the periodic collection of waste is used in practice, it has not been studied in the relevant literature. This paper integrates the periodic inventory routing problem with location decisions for designing healthcare waste management systems and presents a bi-objective mixed-integer nonlinear programming model that minimizes operating costs and risk simultaneously. Due to the complexity of the problem, a two-step approach is proposed. The first stage provides a mixed-integer linear model that generates visiting schedules to source nodes. The second stage offers a Bi-Objective Adaptive Large Neighborhood Search Algorithm (BOALNS) that processes the remaining decisions considered in the problem. The performance of the algorithm is tested on several hypothetical problem instances. Computational analyses are conducted by comparing BOALNS with its other two versions, Adaptive Large Neighborhood Search Algorithm and Bi-Objective Large Neighborhood Search Algorithm (BOLNS). The computational experiments demonstrate that our proposed algorithm is superior to these algorithms in several performance evaluation metrics. Also, it is observed that the adaptive search engine increases the capability of BOALNS to achieve high-quality Pareto-optimal solutions.
Citation - WoS: 20
Citation - Scopus: 22
Bi-Objective Dynamic Weapon-Target Assignment Problem With Stability Measure
(Springer, 2022) Karasakal, Esra; Karasakal, Orhan; Silav, Ahmet; 216553; 06.04. Endüstri Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
In this paper, we develop a new bi-objective model for dynamic weapon-target assignment problem. We consider that the initial weapon assignment plan of defense is disrupted during engagement because of a destroyed air target, breakdown of a weapon system or a new incoming air target. The objective functions are defined as the maximization of probability of no-leaker and the maximization of stability in engagement order of weapon systems. Stability is defined as assigning same air target in sequence in engagement order of a weapon system so that reacquisition and re-tracking of air target are not required by sensors. We propose a new solution procedure to generate updated assignment plans by maximizing efficiency of defense while maximizing stability through swapping weapon engagement orders. The proposed solution procedure generates non-dominated solutions from which defense can quickly choose the most-favored course of action. We solve a set of representative problems with different sizes and present computational results to evaluate effectiveness of the proposed approach.
Citation - WoS: 4
Citation - Scopus: 4
A Bi-Objective Integrated Mathematical Model for Blood Supply Chain: Case of Turkish Red Crescent
(Amer inst Mathematical Sciences-aims, 2023) Yolcu, Vahdi; Satir, Benhur; 54700; 01. Çankaya Üniversitesi; 06. Mühendislik Fakültesi; 06.04. Endüstri Mühendisliği
Various criteria feature in blood supply chain (BSC) designs, where cost-based and time-based are the most commonly found in the literature. In the current study, total annual cost is used together with a new time-based objective. The total time spent in the transportation of blood products is considered as time lost, and weight is given to that time according to the product amount and then normalized with respect to shelf life. In using cost and time objectives, we developed a bi-objective mixed-integer mathematical programming model for the BSC of Turkish Red Crescent (TRC, the singular authority controlling BSC throughout Turkey), including collection, production, and distribution echelons, and also considering bag-type decisions for whole-blood collection. The objective of the study was to propose a BSC design model and solution approach. With all real-life TRC instances resolved optimally, a linear programming relaxation-based heuristic was developed for large-scale problem sizes. Real-life data were obtained from the TRC and the remainder from open-to-public sources. The study's main finding is that cost and time objectives alone produce significantly different designs, whilst using them together to form efficient-frontier solutions for decision-makers adds practical value.
Citation - WoS: 6
Citation - Scopus: 9
Bi-Objective Missile Rescheduling for a Naval Task Group With Dynamic Disruptions
(Wiley, 2019) Karasakal, Orhan; Karasakal, Esra; Silav, Ahmet; 216553; 06.04. Endüstri Mühendisliği; 06. Mühendislik Fakültesi; 01. Çankaya Üniversitesi
This paper considers the rescheduling of surface-to-air missiles (SAMs) for a naval task group (TG), where a set of SAMs have already been scheduled to intercept a set of anti-ship missiles (ASMs). In missile defense, the initial engagement schedule is developed according to the initial state of the defensive and attacking units. However, unforeseen events may arise during the engagement, creating a dynamic environment to be handled, and making the initial schedule infeasible or inefficient. In this study, the initial engagement schedule of a TG is assumed to be disrupted by the occurrence of a destroyed ASM, the breakdown of a SAM system, or an incoming new target ASM. To produce an updated schedule, a new biobjective mathematical model is formulated that maximizes the no-leaker probability value for the TG and minimizes the total deviation from the initial schedule. With the problem shown to be NP-hard, some special cases are presented that can be solved in polynomial time. We solve small size problems by the augmented epsilon-constraint method and propose heuristic procedures to generate a set of nondominated solutions for larger problems. The results are presented for different size problems and the total effectiveness of the model is evaluated.
Citation - WoS: 5
Citation - Scopus: 5
A Blood Distribution Problem With New Transportation Options - an Application for the Turkish Red Crescent
(inderscience Enterprises Ltd, 2019) Azizoglu, Meral; Kurt, Atil; Cetinkaya, Ferda Can; 50129; 01. Çankaya Üniversitesi; 06. Mühendislik Fakültesi; 06.04. Endüstri Mühendisliği
This paper considers the blood distribution problem in the Central Anatolian Regional Blood Centre of the Turkish Red Crescent (TRC) and proposes several demand satisfaction options considering the irradiation centres, urgent demands, and product availability. Our aim is to maximise the total weighted blood demand satisfaction. To address the problem, we develop a mixed integer linear programming model and propose a hybrid genetic algorithm (HGA). The results of our experiments have revealed that the mathematical model cannot handle even small sized problem instances in reasonable times; however, the hybrid genetic algorithm is capable of handling complex daily operations of the Turkish Red Crescent.

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