Mühendislik Fakültesi / Faculty of Engineering

Permanent URI for this collectionhttps://hdl.handle.net/11727/1401

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Author: search.filters.author.Altiparmak, Fulyasearch.filters.applied.f.publicationcategory: search.filters.publicationcategory.Makale - Ulusal Hakemli Dergi

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    Heterogeneous Vehicle Routing Problem with Simultaneous Pickup and Delivery: Mathematical Formulations and A Heuristic Algorithm
    (2015) Kececi, Baris; Altiparmak, Fulya; Kara, Imdat; 0000-0002-2730-5993; AAF-7020-2021; AAC-4793-2019; ABH-1078-2021; F-1639-2011
    One of the most important operational decisions in the logistics management is to determine the vehicle routes serving the customers. The Vehicle Routing Problem (VRP) can be defined as the determination of the optimal routes which meet the delivery (or pickup) demands from the depot to the customers. In the real life applications of logistics, vehicles in a fleet may differ from each other. In addition, the requirements arising from customers/goods may reveal the necessity to use different vehicles. Besides, companies do care more about the management of reverse flow of products, semi-finished and raw materials because of their economic benefits and as well as legal and environmental liabilities. In this paper, a variant of the VRP is considered with heterogeneous fleet of vehicles and simultaneous pickup and delivery. This problem is referred to Heterogeneous Vehicle Routing Problem with Simultaneous Pickup and Delivery (HVRPSPD). The HVRPSPD can be defined as determining the routes and the vehicle types on each route while minimizing the total cost. In this paper, a polynomial sized flow-based mathematical model is proposed for the HVRPSPD. Since the HVRPSPD is in the class of NP-hard problems, it is difficult to find the optimal solution in a reasonable time even for the moderate size problems. Therefore, a simple and constructive heuristic algorithm is proposed to solve the medium and large scale HVRPSPD s. This algorithm is the adaptation of very well-known Clarke-Wright Savings approach, which has originally developed for the VRP, to the HVRPSPD. The performances of the proposed mathematical model and the heuristic algorithm have been examined on the test problems.
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    A goal programming approach for multi objective, multi-trips and time window routing problem in home health care service
    (2021) Dengiz, Asiye Ozge; Atalay, Kumru Didem; Altiparmak, Fulya
    The structure of services in the health sector is changed by the epidemic diseases affecting the world, the population growth and developing technologies. Due to the advantages it provides, home health care (HHC) services are increasingly being demanded by patients. With the in-crease in demand for HHC, the interest of researchers in Home Health Care Routing Problem (HHCRP) is also increasing. In this study, HHCRP has been studied based on information gathered from a relevant unit of a State Hospital providing HHC services in Ankara. Due to the limited resources in the hospital under consideration, vehicles often need to be used for multiple rounds. Thus, the HHCRP is considered as a multi-tour routing problem. Besides, the problem has been created with time window constraints in order to ensure that the demands of the patients are met on time. Meantime, meeting all the patient demands and reducing the environmental impacts are two important goals in HHCRP. The reduction of the environmental impacts can be achieved by minimizing the carbon emission of the vehicles used in the HHC. Thus, the problem addressed in this study has been defined as a multi-objective, multi-trip and time-windows home healthcare routing problem (MTTW-HHCRP). Weighted goal programming (GP) method is used to solve the proposed problem. Test problems are randomly generated based on the data and the information obtained from the hospital in Ankara, and the solutions obtained through scenario analysis are evaluated to guide the decision-making process.