Grigorios D. Konstantakopoulos

Mr. Grigorios D. Konstantakopoulos

National Technical University of Athens (NTUA)
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Research Focus & Metrics

Academic Career Length

9Years (2018-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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9 September 2020 in Operational Research
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Grigorios D. KonstantakopoulosGrigorios D. Konstantakopoulos
Grigorios D. Konstantakopoulos
Sotiris GayialisSotiris Gayialis
Sotiris Gayialis
Evripidis KechagiasEvripidis Kechagias
Evripidis Kechagias

7 January 2022 in Logistics
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Journal Article
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Sotiris GayialisSotiris Gayialis
Sotiris Gayialis
Evripidis KechagiasEvripidis Kechagias
Evripidis Kechagias
Grigorios D. KonstantakopoulosGrigorios D. Konstantakopoulos
Grigorios D. Konstantakopoulos
Georgios PapadopoulosGeorgios Papadopoulos
Georgios Papadopoulos
Background: Reverse supply chains of machinery and equipment face significant challenges, and overcoming them is critical for effective customer service and sustainable operation. Maintenance and repair services, strongly associated with the reverse movement of equipment, are among the most demanding reverse supply chain operations. Equipment is scattered in various locations, and multiple suppliers are involved in its maintenance, making it challenging to manage the related reverse supply chain operations. Effective maintenance is essential for businesses-owners of the equipment, as reducing costs while improving service quality helps them gain a competitive advantage. Methods: To enhance reverse supply chain operations related to equipment maintenance, this paper presents the operational framework, the methodological approach, and the architecture for developing a system that covers the needs for predictive maintenance in the service supply chain. It is based on Industry 4.0 technologies, such as the Internet of things, machine learning, and cloud computing. Results: As a result of the successful implementation of the system, effective equipment maintenance and service supply chain management is achieved supporting the reverse supply chain. Conclusions: This will eventually lead to fewer good-conditioned spare part replacements, just in time replacements, extended equipment life cycles, and fewer unnecessary disposals.

1 March 2022 in Operational Research
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Journal Article
Closed access
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Sotiris GayialisSotiris Gayialis
Sotiris Gayialis
Evripidis KechagiasEvripidis Kechagias
Evripidis Kechagias
Grigorios D. KonstantakopoulosGrigorios D. Konstantakopoulos
Grigorios D. Konstantakopoulos

26 September 2020 in Algorithms
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Grigorios D. KonstantakopoulosGrigorios D. Konstantakopoulos
Grigorios D. Konstantakopoulos
Sotiris GayialisSotiris Gayialis
Sotiris Gayialis
Evripidis KechagiasEvripidis Kechagias
Evripidis Kechagias
Georgios PapadopoulosGeorgios Papadopoulos
Georgios Papadopoulos
ITIlias P. Tatsiopoulos
Ilias P. Tatsiopoulos
The Vehicle Routing Problem with Time Windows (VRPTW) is an NP-Hard optimization problem which has been intensively studied by researchers due to its applications in real-life cases in the distribution and logistics sector. In this problem, customers define a time slot, within which they must be served by vehicles of a standard capacity. The aim is to define cost-effective routes, minimizing both the number of vehicles and the total traveled distance. When we seek to minimize both attributes at the same time, the problem is considered as multiobjective. Although numerous exact, heuristic and metaheuristic algorithms have been developed to solve the various vehicle routing problems, including the VRPTW, only a few of them face these problems as multiobjective. In the present paper, a Multiobjective Large Neighborhood Search (MOLNS) algorithm is developed to solve the VRPTW. The algorithm is implemented using the Python programming language, and it is evaluated in Solomon’s 56 benchmark instances with 100 customers, as well as in Gehring and Homberger’s benchmark instances with 1000 customers. The results obtained from the algorithm are compared to the best-published, in order to validate the algorithm’s efficiency and performance. The algorithm is proven to be efficient both in the quality of results, as it offers three new optimal solutions in Solomon’s dataset and produces near optimal results in most instances, and in terms of computational time, as, even in cases with up to 1000 customers, good quality results are obtained in less than 15 min. Having the potential to effectively solve real life distribution problems, the present paper also discusses a practical real-life application of this algorithm.

29 November 2020 in Systems
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Evripidis KechagiasEvripidis Kechagias
Evripidis Kechagias
Sotiris GayialisSotiris Gayialis
Sotiris Gayialis
Grigorios D. KonstantakopoulosGrigorios D. Konstantakopoulos
Grigorios D. Konstantakopoulos
Georgios PapadopoulosGeorgios Papadopoulos
Georgios Papadopoulos
Today, there is a great need for greener urban freight transportations due to their ever-increasing environmental impact. The planet’s climate has been significantly affected as the temperature is constantly rising and extreme weather events are occurring more and more often. Aiming to reduce the environmental impact of freight transportation in urban areas, an advanced vehicle routing and scheduling system for improving urban freight transportations, has been developed. This paper presents the functionality of the advanced system, while also analyzing its subsystems and demonstrating its use in a case study. The system is provided as an integrated cloud-based software to support the needs of logistics companies, in order to efficiently schedule their deliveries and perform the routing of their vehicles. The utilized multi-objective algorithm produces solutions that minimize either the distribution cost or the environmental emissions or a combination of these parameters. An application of the system is performed for validation purposes, concerning the comparison of the system’s results with corresponding real-life data provided by a medium-sized logistics company. The results of the testing reveal its significant contribution to the reduction of the environmental impact of the company’s distribution services.

28 September 2018 in Springer Proceedings in Business and Economics (SPBE)
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Book Chapter
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Sotiris GayialisSotiris Gayialis
Sotiris Gayialis
Grigorios D. KonstantakopoulosGrigorios D. Konstantakopoulos
Grigorios D. Konstantakopoulos
ITIlias P. Tatsiopoulos
Ilias P. Tatsiopoulos