Endüstri Mühendisliği Bölümü

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Citation - WoS: 16
Citation - Scopus: 24
A decision support system for locating weapon and radar positions in stationary point air defence
(Springer, 2012) Tanerguclu, Turker; Aygüneş, Haluk; Maras, Hakan; Gencer, Cevriye; Aygunes, Haluk; 7671; 57149; Endüstri Mühendisliği
In this study, a decision support system (DSS) based on the interactive use of location models and geographical information systems (GIS) was developed to determine the optimal positions for air defence weapons and radars. In the location model, the fire units are considered as the facilities to be located and the possible approach routes of air vehicles are treated as demand points. Considering the probability that fire by the units will miss the targets, the objective of the problem is to determine the positions that provide coverage of the approach routes of the maximum number of weapons while considering the military principles regarding the tactical use and deployment of units. In comparison with the conventional method, the proposed methodology presents a more reliable, faster, and more efficient solution. On the other hand, owing to the DSS, a battery commander who is responsible for air defence becomes capable of determining the optimal weapon and radar positions, among the alternative ones he has identified, that cover the possible approach routes maximally. Additionally, he attains the capability of making such decisions in a very short time without going to the field over which he will perform the defence and hence without being subject to enemy threats. In the decision support system, the digital elevation model is analysed using Map Objects 2.0, the mathematical model is solved using LINGO 4.0 optimization software, and the user interface and data transfer are supported by Visual Basic 6.0.
Citation - WoS: 49
Citation - Scopus: 54
A profit-oriented mathematical model for hazardous waste locating-routing problem
(Elsevier Sci Ltd, 2018) Aydemir-Karadag, Ayyuce; 116059
Hazardous waste management (HWM) deals with the safe, efficient and cost effective collection, transportation, treatment and disposal of wastes. This paper presents a profit-oriented mixed integer mathematical model for the hazardous waste location-routing problem, which incorporates the energy recovery from waste and the application of the polluter pays principle. The suggested model decides on the locations and numbers of recycling, incineration, sterilization, interim storage and disposal centers and on how to transfer various types of hazardous waste and waste residues among these centers from the perspective of environmental protection. The proposed model was implemented in a real life case study and tested on various hypothetical problem instances. In addition, an extended formulation was developed on a rolling horizon basis through the objective function of Net Present Value (NPV) to analyze the overall profitability of the entire HWM system for long-term planning and a sensitivity study was conducted on different interest rates. The results show that the model is applicable to real-life waste management systems and it can provide effective solutions for large-scale HWM problems. (C) 2018 Elsevier Ltd. All rights reserved.
Citation - WoS: 28
Citation - Scopus: 49
A technology readiness levels (TRLs) calculator software for systems engineering and technology management tool
(Elsevier Sci Ltd, 2010) Altunok, Taner; Altunok, Taner; Cakmak, Tanyel; Makine Mühendisliği
Turkish defense industry and policy makers seek effective and successful system development programs by implementing a validation mechanism to verify the maturity of new technologies being developed in national laboratories and industry. Technology Readiness Levels (TRLs) developed by NASA as a general metric of technology advancement and it has been widely accepted as a systems engineering and technology management metric tool. In order to explore the sufficiency of this tool, first of all, academic and applicable studies of army and civil organizations have been searched out and the lessons learned have been analyzed in this study. Thereafter, questionnaires of awareness of TRLs and TRL Calculator have been applied to defense firms in Ankara, and interviews held with the technology developers, firms' speakers and defense authorities. Finally, the applicable algorithm of TRL calculator has been recommended for Turkish defense industry. (C) 2009 Elsevier Ltd. All rights reserved.
Citation - WoS: 9
Citation - Scopus: 17
A truck loading problem
(Pergamon-elsevier Science Ltd, 2010) Yuceer, Umit; Yüceer, Ümit; Ozakca, Arif; Endüstri Mühendisliği
A vehicle with m compartments transports q different products of various sizes from a source to n different destinations. The operational problem is how to load the compartments of the vehicle so that the replenishment time is maximized for a given route of destinations. A mixed integer linear programming model is developed for this class of problems. An investigation of the structure of the model reveals that a subproblem can be obtained in the form of a weighted distribution problem. Consequently, a simple subalgorithm finds an integer solution to this subproblem. The main algorithm bisects the interval of uncertainty until it becomes sufficiently small. There is another subalgorithm to test whether a feasible solution exists in the final interval of uncertainty by solving a Phase I problem. Our numerical experience has shown its computational efficiency and the quality of the solutions obtained. A problem of size 30 can be solved by this method in a fraction of a second. Further, an optimal solution is obtained in 82% of the randomly chosen problems. (C) 2010 Elsevier Ltd. All rights reserved.
Citation - WoS: 6
Citation - Scopus: 7
An approximation for kanban controlled assembly systems
(Springer, 2011) Topan, Engin; Topan, Engin; Avsar, Zeynep Muge; 164129; Endüstri Mühendisliği
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: 96
Citation - Scopus: 115
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
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 - WoS: 17
Citation - Scopus: 17
Bi-objective dynamic weapon-target assignment problem with stability measure
(Springer, 2022) Silav, Ahmet; Karasakal, Orhan; Karasakal, Esra; Karasakal, Orhan; 216553; Endüstri Mühendisliği
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: 15
Citation - Scopus: 17
Determination of equivalent warehouses in humanitarian logistics by reallocation of multiple item type inventories
(Elsevier, 2021) Demirbas, Sefika; Ertem, Mustafa Alp; Ertem, Mustafa Alp; 52460; Endüstri Mühendisliği
Prepositioning freight containers for storage of relief supplies can be considered an alternative to warehousing with shelves. Recently, 25 container warehouses are located in different cities in Turkey to deliver relief supplies to beneficiaries quickly. We take this existing situation as given and investigate if this investment could be utilised better. The available inventory (i.e., tents, beds, blankets) in these container warehouses is currently not used efficiently. Some warehouses store one type of item and none from other types. Therefore, several warehouses must be activated during a response operation to fully satisfy the beneficiaries' needs for each relief item type. We aim to investigate the benefits of operating equivalent (i.e., a proper inventory level from each relief item type) warehouses while reallocating a total available inventory for better coordination. A locationreallocation type of mathematical model is tested with real-life data from past earthquakes. Three to eight container warehouses are recommended to be converted to an equivalent type. The results indicate potential savings for the proposed model, and this potential is more visible in large-scale demand instances than in small ones.
Citation - WoS: 37
Citation - Scopus: 54
Effects of circumferential pick spacing on boom type roadheader cutting head performance
(Pergamon-elsevier Science Ltd, 2005) Eyyuboglu, EM; Bolukbasi, N
Effects of equal and unequal circumferential pick spacing on the performance of boom type roadheaders having cylindrical cutting heads are investigated. For this purpose, two experimental cutting heads with equal and unequal circumferential spacing are designed and manufactured. The cutting head with unequal circumferential spacing is specifically designed to prevent tool-holder overlap at the nose section. Manufacturing difficulties associated with equal circumferential pick spacing due to tool-holder overlap are discussed with solid modeling and practical applications. The heads are tested at Park Cayirhan Coal Mine in Turkey and their cutting performances are analysed. Although better cutting performance for equal circumferential spacing are predicted by force-balance analysis, in situ measurements of instantaneous (net) traversing speed and cutting rate, pick consumption rate and machine vibration show that no significant difference exists between the performances of the two cutting heads. (C) 2005 Elsevier Ltd. All rights reserved.
Citation - WoS: 2
Citation - Scopus: 3
Effects of privatization: A case study from Cayirhan coal district, Turkey
(Elsevier Sci Ltd, 2006) Eyyuboglu, E. Mustafa
Privatization of lignite coal-fired power plants in Turkey began in the middle of 1990 and is still an ongoing process. Among the 10 power plants offered to bidders in 1996, only Cayirhan power plant bundled with the coal mine was privatized. Considerable improvements have been obtained following the privatization of both the power plant and the coal mine. In view of its success, it is considered that Cayirhan experience could serve as a model for further privatization in energy sector, planned to be completed by the end of 2006 according to the agenda issued by government. This paper deals with the overall improvements following the privatization of both the power plant and the coal mine. In particular, mechanized roadway drivage performances before and after privatization are compared in order to highlight the specific effects of privatization in this area. It is found that competition, organizational and operational changes are the main causes of improvements attained in the post-privatization period. (c) 2005 Elsevier Ltd. All rights reserved.
Citation - WoS: 8
Citation - Scopus: 12
Estimating parameters of a multiple aoutoregressive model by the modified maximum likelihood method
(Elsevier, 2010) Bayrak, Oezlem Tuerker; Akkaya, Aysen D.; 56416; 2337
We consider a multiple autoregressive model with non-normal error distributions, the latter being more prevalent in practice than the usually assumed normal distribution. Since the maximum likelihood equations have convergence problems (Puthenpura and Sinha, 1986) [11], we work Out modified maximum likelihood equations by expressing the maximum likelihood equations in terms of ordered residuals and linearizing intractable nonlinear functions (Tiku and Suresh, 1992) [8]. The solutions, called modified maximum estimators, are explicit functions of sample observations and therefore easy to compute. They are under some very general regularity conditions asymptotically unbiased and efficient (Vaughan and Tiku, 2000) [4]. We show that for small sample sizes, they have negligible bias and are considerably more efficient than the traditional least Squares estimators. We show that Our estimators are robust to plausible deviations from an assumed distribution and are therefore enormously advantageous as compared to the least squares estimation. We give a real life example. (C) 2009 Elsevier B.V. All rights reserved.
Citation - WoS: 11
Citation - Scopus: 15
Intermodal transportation in humanitarian logistics with an application to a Turkish network using retrospective analysis
(Elsevier, 2022) Ertem, Mustafa Alp; Ertem, Mustafa Alp; Akdogan, Muharrem Altan; Kahya, Melike; 52460; Endüstri Mühendisliği
In the event of disruptions in a transportation network following a disaster, humanitarian organizations find it challenging to provide basic requirements for beneficiaries. Demand may be met using intermodal transportation as an alternative when the unimodal transportation infrastructure is damaged. This study proposes a mathematical model for utilizing intermodal transportation using 40 ft standard containers while delivering relief supplies by road, rail, and sea modes. The proposed model is a capacitated multi-period multicommodity intermodal network flow model in which relief supplies are delivered to beneficiaries in three echelons (i.e., supply, intermodal hub, and demand). The Turkish Disaster and Emergency Management Presidency's container warehouses (i.e., supply), logistics centers and container ports (i.e., intermodal hubs) are utilized to test the mathematical model with real-life demand parameters. Retrospective analysis was performed to determine the most frequently used container warehouses, logistics centers, and origin-destination pairs. Hence, an increase in operational capacity and infrastructure reinforcement is recommended to mitigate the effects of future disasters. We found that intermodal transportation is more robust to network disruptions in rapidly delivering relief supplies. We observed that intermodal transportation is utilized in disasters with more than 50,000 beneficiaries or disrupted unimodal infrastructure. For instance, after the future Istanbul earthquake, it would be impossible to deliver the relief materials only by road transportation within the urgent response period. Thus, the benefits of intermodal transportation in humanitarian logistics are more visible in large-scale disasters in which transportation resources are scarce, and transportation infrastructure is more likely to be destroyed.
Citation - WoS: 285
Citation - Scopus: 347
Models, solutions and enabling technologies in humanitarian logistics
(Elsevier Science Bv, 2015) Ozdamar, Linet; Ertem, Mustafa Alp; Ertem, Mustafa Alp; 52460; Endüstri Mühendisliği
We present a survey that focuses on the response and recovery planning phases of the disaster lifecycle. Related mathematical models developed in this area of research are classified in terms of vehicle/network representation structures and their functionality. The relationships between these characteristics and model size are discussed. The review provides details on goals, constraints, and structures of available mathematical models as well as solution methods. In this review, information systems applications in humanitarian logistics are also surveyed, since humanitarian logistics models and their solutions need to be integrated with information technology to enable their use in practice. (C) 2014 Elsevier B.V. All rights reserved.
Citation - WoS: 2
Citation - Scopus: 3
Multiobjective aerial surveillance over disjoint rectangles
(Pergamon-elsevier Science Ltd, 2020) Karasakal, Orhan; Karasakal, Orhan; Karasakal, Esra; Maras, Guliz; 216553; Endüstri Mühendisliği
In Aerial Surveillance Problem (ASP), an air platform with surveillance sensors searches a number of rectangular areas by covering the rectangles in strips and turns back to base where it starts. In this paper, we present a multiobjective extension to ASP, for which the aim is to help aerial mission planner to reach his/her most preferred solution among the set of efficient alternatives. We consider two conflicting objectives that are minimizing distance travelled and maximizing minimum probability of target detection. Each objective can be used to solve single objective ASPs. However, from mission planner's perspective, there is a need for simultaneously optimizing both objectives. To enable mission planner reaching his/her most desirable solution under conflicting objectives, we propose exact and heuristic methods for multiobjective ASP (MASP). We also develop an interactive procedure to help mission planner choose the most satisfying solution among all Pareto optimal solutions. Computational results show that the proposed methods enable mission planner to capture the tradeoffs between the conflicting objectives for large number of alternative solutions and to eliminate the undesirable solutions in small number of iterations.
Citation - WoS: 8
Citation - Scopus: 12
Pooling through lateral transshipments in service parts systems
(Elsevier Science Bv, 2012) Satir, Benhur; Satır, Benhür; Savasaneril, Secil; Serin, Yasemin; 54700; 125953; Endüstri Mühendisliği
We study the inventory management problem of a service center operating in a decentralized service parts network. The service centers collaborate through inventory and service pooling, and through sharing information on the inventory status. Upon demand arrival, a service center may request a part from the other center, in which case a payment is made. Under this competitive and collaborative environment, we first characterize the optimal operating policy of an individual service center. Through computational analysis we identify the conditions under which pooling is most beneficial to the service center, and make an assessment of different pooling strategies which are commonly adopted in practice and in the literature. Finally, we analyze the effect of interaction between the centers on the benefit of pooling. (C) 2012 Elsevier B.V. All rights reserved.
Citation - WoS: 41
Citation - Scopus: 46
Pre-positioning of relief items in humanitarian logistics considering lateral transhipment opportunities
(Elsevier Science inc, 2017) Baskaya, Serhat; Ertem, Mustafa Alp; Ertem, Mustafa Alp; Duran, Serhan; 52460; 164958; Endüstri Mühendisliği
The main objective of this study is to investigate the inclusion of lateral transhipment opportunities into the humanitarian relief chain and to examine the effect of different parameters on minimizing the average distance travelled per item while serving the beneficiaries. Direct shipment model (DT), lateral transhipment model (LTSP) and maritime lateral transhipment model (MLTSP) are developed and compared between each other by using a real life earthquake scenario prepared for the city of Istanbul by JICA (Japanese International Cooperation Agency). Developed mathematical models decide on the locations and number of disaster relief facilities, quantity of relief items to hold at those facilities, and quantity of lateral transhipment between the facilities. Vulnerability of the roads and heterogeneous capacitated facilities are also considered. It can be concluded that both LTSP and MLTSP models gave better results than DT model and lateral transhipment option helps beneficiaries to obtain relief items faster and with higher service level. (C) 2016 Elsevier Ltd. All rights reserved.
Citation - WoS: 63
Citation - Scopus: 84
Removal of ammonium and phosphate from the supernatant of anaerobically digested waste activated sludge by chemical precipitation
(Elsevier Sci Ltd, 2009) Uludag-Demirer, Sibel; Othman, Maazuza; 45685
The removal of ammonium (NH4+) and phosphate (PO43-) from supernatant of anaerobic digestion by magnesium ammonium phosphate (MAP) formation was Studied. To be able to find out the loss of NH4+ by its transformation to NH3, rates of NH4+ removal by aeration and by MAP formation combined with aeration were compared. NH4+ removal by aeration was found to be insignificant. The kinetics of MAP formation was fast. The removal rate of NH4+ and Mg2+ was the smallest and the largest, respectively based on rate constants calculated. The removal of NH4+ showed sensitivity to Mg2+ and PO43- concentrations and controlled the purity of MAP precipitate. The removal of PO43- was found to be Sensitive to mainly Mg2+ ion. These results also indicated that as the supernatant Solution became more saturated in terms of MAP forming ions, the effect of pH increase became insignificant in the removal of ions from the solution. (C) 2009 Elsevier Ltd. All rights reserved.
Citation - WoS: 19
Citation - Scopus: 21
Shipment consolidation with two demand classes: Rationing the dispatch capacity
(Elsevier Science Bv, 2018) Satir, Benhur; Satır, Benhür; Erenay, Fatih Safa; Bookbinder, James H.; 54700; Endüstri Mühendisliği
We analyze the problem faced by a logistics provider that dispatches shipment orders (parcels or larger packages) of two order classes, viz. expedited and regular. Shipment orders arrive according to a compound Poisson process for each class. Upon an arrival, the logistics provider may continue consolidating arriving orders by paying a holding cost. Alternatively, the provider may dispatch, at a fixed cost, a vehicle containing (a portion of) the load consolidated so far. In addition, the provider must specify the composition of each dispatch by allocating (rationing) the volume of the vehicle between expedited and regular shipment orders. We model this problem as a continuous-time Markov Decision Process and minimize the expected discounted total cost. We prove the existence of quantity-based optimal threshold policies under particular conditions. We also structurally analyze the thresholds of these optimal policies. Based on these structural properties, we develop an efficient solution approach for large problem instances which are difficult to solve using the conventional policy-iteration method. For two real-life applications, we show that the quantity-based threshold policies derived using the proposed approach outperform the time policies used in practice. (C) 2018 Elsevier B.V. All rights reserved.
Citation - Scopus: 22
Using announcement options in the bid construction phase for disaster relief procurement
(2012) Ertem, M.A.; Buyurgan, N.; Pohl, E.A.; 52460
This paper presents an analysis of the bid construction phase of procurement auctions in disaster relief and humanitarian logistics. Substitution and partial fulfillment options are presented in formulations to allow bidders with fewer inventories to offer substitute item types and partial bids in auctions. During the auction announcement phase, a coordinating platform for disaster locations (i.e., auctioneer) allows substitution and partial fulfillment options to the relief suppliers (i.e., bidders) when acceptable. Thus, suppliers with fewer inventories can offer substitute item types and participate in more auctions by partially bidding. A genetic algorithm, a simulated annealing algorithm and an integer program are used for the analysis of the bid construction phase with different announcement options. Heuristic solution techniques and an IP formulation help understand the dynamics of the bid construction problem. It is shown that the addition of substitution and partial fulfillment options is essential to diversify and increase the usable capacity of the supplier base. Additionally, the partial fulfillment option enables better usage of supplier inventories in an environment with scarce supplies. © 2012 Elsevier Ltd.

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