Endüstri Mühendisliği Bölümü Yayın Koleksiyonu

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

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  • Article
    Citation - WoS: 8
    Citation - Scopus: 9
    Intermodal Humanitarian Logistics Using Unit Load Devices
    (Springer Heidelberg, 2022) Kavlak, Hasan; Ertem, Mustafa Alp; Satir, Benhur
    Intermodal freight transportation facilitates today's global trade. The benefits of intermodal freight transportation have been studied and are more observable in commercial logistics; however, the potential benefits of humanitarian logistics have not been thoroughly investigated. This research aims to present a resilient transportation framework by modeling intermodal transportation utilizing interoperable loading devices during disaster responses. We developed an integer programming model based on a time-space network by considering route and vehicle availabilities that are allowed to change with time. We consider vehicles with varying capacities in three transportation modes (i.e., ground, maritime, and air). The contribution of this study is threefold: (1) Two compatible unit load devices are proposed for humanitarian logistics; (2) a mathematical model that includes integer variable representation for vehicle fleets in different transportation modes is developed; and (3) intermodal transportation is compared with single-mode transportation using a real-life dataset. Our main results are as follows: In terms of cost, intermodal transportation is effective when demand occurs in consecutive periods and response time is short. Inventory is held more in intermodal transportation when it is cost-effective to use transportation modes with large capacities. Thus, the benefits of the responsiveness of intermodal transportation outweigh the costs of mode interchange and inventory holding for sudden-onset disasters where quick responses are needed within a short time.
  • Article
    Citation - WoS: 24
    Citation - Scopus: 27
    Bi-Objective Adaptive Large Neighborhood Search Algorithm for the Healthcare Waste Periodic Location Inventory Routing Problem
    (Springer Heidelberg, 2022) Aydemir-Karadag, Ayyuce
    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.
  • Article
    Citation - WoS: 66
    Citation - Scopus: 85
    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
    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.
  • Article
    Citation - WoS: 98
    Citation - Scopus: 117
    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.
    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.