The Experts below are selected from a list of 129 Experts worldwide ranked by ideXlab platform

Nikolas Geroliminis - One of the best experts on this subject based on the ideXlab platform.

  • An integrated optimization-simulation framework for vehicle and personnel relocations of electric carsharing systems with reservations
    Transportation Research Part B: Methodological, 2017
    Co-Authors: Burak Boyaci, Konstantinos G. Zografos, Nikolas Geroliminis
    Abstract:

    One-way electric vehicle carsharing systems are receiving increasing attention due to their mobility, environmental, and societal benefits. One of the major issues faced by the operators of these systems is the optimization of the relocation operations of personnel and vehicles. These relocation operations are essential in order to ensure that vehicles are available for use at the right place at the right time. Vehicle availability is a key indicator expressing the level of service offered to customers. However, the relocation operations, that ensure this availability, constitute a major cost component for the provision of these services. Therefore, clearly there is a trade-off between the cost of vehicle and personnel relocation and the level of service offered. In this paper we are developing, solving, and applying, in a real world context, an integrated multi-objective mixed integer linear programming (MMILP) optimization and discrete event simulation framework to optimize Operational decisions for vehicle and personnel relocation in a carsharing system with reservations. We are using a clustering procedure to cope with the dimensionality of the Operational Problem without compromising on the quality of the obtained results. The optimization framework involves three mathematical models: (i) station clustering, (ii) operations optimization and (iii) personnel flow. The output of the optimization is used by the simulation in order to test the feasibility of the optimization outcome in terms of vehicle recharging requirements. The optimization model is solved iteratively considering the new constraints restricting the vehicles that require further charging to stay in the station until the results of the simulation are feasible in terms of electric vehicles’ battery charging levels. The application of the proposed framework using data from a real world system operating in Nice, France sheds light to trade-offs existing between the level of service offered, resource utilization, and certainty of fulfilling a trip reservation.

  • a simulation framework for the Operational Problem of one way car sharing systems
    2014
    Co-Authors: Burak Boyaci, Nikolas Geroliminis, Konstantinos G. Zografos
    Abstract:

    Car-sharing systems provide an attractive transportation alternative to their users with beneficial societal, environmental, and energy impacts. Alternative types of Operational concepts of car-sharing systems have been proposed that are in operation around the world. One of these Operational concepts allows for vehicles to be dropped at any station. The one-way car-sharing systems offer significant advantages to the users due to their flexibility. However, this flexibility may lead to accumulation and shortage of vehicles at certain stations, that have limited capacity. To cope with this Problem, operators of one-way car-sharing systems need to perform costly relocation operations. Electric vehicles apply an additional constraint of charging levels in the Operational framework. This research is focused on the modelling of vehicle relocation decisions of one-way electric car-sharing systems. A MILP formulation is proposed in order to optimally relocate vehicles and personnel among the system stations , and to optimally assign relocation personnel to shifts. The proposed model is solved using real data from Nice, France and provides the opportunity to examine the trade-off between Operational cost and vehicle availability.

Metin Celik - One of the best experts on this subject based on the ideXlab platform.

  • a maritime research concept through establishing ship Operational Problem solution shipos centre via information technologies integrated with or ms
    Procedia - Social and Behavioral Sciences, 2015
    Co-Authors: Omer Soner, Emre Akyuz, Metin Celik
    Abstract:

    The recent developments in maritime transportation have been leading to integrate advance management systems into ship fleet operations. Design and implementations of such systems are highly required managerial skills and methodological tools. This study conceptualizes a ship fleet Operational Problem solution centre (SHIPOS) to systematically analyse the various cases, facts and figures promoting with comprehensive outcomes. The SHIPOS initiative has been established to additionally support the sub-tasks of WP#1 (database network, industry information sharing network, research network) within research project entitled “Human Reliability Analysis and Monitoring System Proposal in Shipboard Operations (H-RAMS)” (Project no: 114M352) supported by the Scientific and Technological Research Council of Turkey (TUBITAK). Besides the feedbacks from ship operating environment, the solution centre also considers the technology expectations specified in the recent global initiatives (i.e. Horizon’2020, IMO strategies) to predict the required future maritime innovations. As another aspect, the methodological background of solution centre takes the advantage of OR/MS techniques comply with the focused Problems. Consequently, this paper presents the critical milestones of providing information technology solutions to ship fleet management such as data acquisition, modelling, shipboard integration, verification, etc. in a continuous maritime research concept.

  • World Conference on Technology, Innovation and Entrepreneurship A Maritime Research Concept through Establishing Ship Operational Problem Solution (Shipos) Centre via Information Technologies Integrated With or/Ms
    2015
    Co-Authors: Omer Soner, Emre Akyuz, Metin Celik
    Abstract:

    The recent developments in maritime transportation have been leading to integrate advance management systems into ship fleet operations. Design and implementations of such systems are highly required managerial skills and methodological tools. This study conceptualizes a ship fleet Operational Problem solution centre (SHIPOS) to systematically analyse the various cases, facts an d figures promoting with comprehensive outcomes. The SHIPOS initiative has been established to additionally support the sub-tasks of WP#1 (database network, industry information sharing netw ork, research network) within research project entitled “Human Reliability Analysis and Monitoring System Proposal in Shipboard Operations (H-RAMS)” (Project no: 114M352) s upported by the Scientific and Technological Research Council of Turkey (TUBITAK). Besides the feedbacks from ship operating environment, the solution centre also considers the technology expectations specified in the recent global initiatives (i.e. Horizon’2020, IMO strategies) to predict the required future maritime innovations. As another aspect, the methodological background of solution centre takes the advantage of OR/MS techniques comply with the focused Problems. Consequently, this paper presents the critical milestones of providing information technology solutions to ship fleet management such as data acquisition, modelling, shipboard integration, verification, etc. in a continuous maritime research concept.

Burak Boyaci - One of the best experts on this subject based on the ideXlab platform.

  • An integrated optimization-simulation framework for vehicle and personnel relocations of electric carsharing systems with reservations
    Transportation Research Part B: Methodological, 2017
    Co-Authors: Burak Boyaci, Konstantinos G. Zografos, Nikolas Geroliminis
    Abstract:

    One-way electric vehicle carsharing systems are receiving increasing attention due to their mobility, environmental, and societal benefits. One of the major issues faced by the operators of these systems is the optimization of the relocation operations of personnel and vehicles. These relocation operations are essential in order to ensure that vehicles are available for use at the right place at the right time. Vehicle availability is a key indicator expressing the level of service offered to customers. However, the relocation operations, that ensure this availability, constitute a major cost component for the provision of these services. Therefore, clearly there is a trade-off between the cost of vehicle and personnel relocation and the level of service offered. In this paper we are developing, solving, and applying, in a real world context, an integrated multi-objective mixed integer linear programming (MMILP) optimization and discrete event simulation framework to optimize Operational decisions for vehicle and personnel relocation in a carsharing system with reservations. We are using a clustering procedure to cope with the dimensionality of the Operational Problem without compromising on the quality of the obtained results. The optimization framework involves three mathematical models: (i) station clustering, (ii) operations optimization and (iii) personnel flow. The output of the optimization is used by the simulation in order to test the feasibility of the optimization outcome in terms of vehicle recharging requirements. The optimization model is solved iteratively considering the new constraints restricting the vehicles that require further charging to stay in the station until the results of the simulation are feasible in terms of electric vehicles’ battery charging levels. The application of the proposed framework using data from a real world system operating in Nice, France sheds light to trade-offs existing between the level of service offered, resource utilization, and certainty of fulfilling a trip reservation.

  • a simulation framework for the Operational Problem of one way car sharing systems
    2014
    Co-Authors: Burak Boyaci, Nikolas Geroliminis, Konstantinos G. Zografos
    Abstract:

    Car-sharing systems provide an attractive transportation alternative to their users with beneficial societal, environmental, and energy impacts. Alternative types of Operational concepts of car-sharing systems have been proposed that are in operation around the world. One of these Operational concepts allows for vehicles to be dropped at any station. The one-way car-sharing systems offer significant advantages to the users due to their flexibility. However, this flexibility may lead to accumulation and shortage of vehicles at certain stations, that have limited capacity. To cope with this Problem, operators of one-way car-sharing systems need to perform costly relocation operations. Electric vehicles apply an additional constraint of charging levels in the Operational framework. This research is focused on the modelling of vehicle relocation decisions of one-way electric car-sharing systems. A MILP formulation is proposed in order to optimally relocate vehicles and personnel among the system stations , and to optimally assign relocation personnel to shifts. The proposed model is solved using real data from Nice, France and provides the opportunity to examine the trade-off between Operational cost and vehicle availability.

Mark Andrews - One of the best experts on this subject based on the ideXlab platform.

  • A Common Operational Problem in DNS Servers - Failure To Communicate.
    2019
    Co-Authors: Mark Andrews, Ray Bellis
    Abstract:

    The DNS is a query / response protocol. Failing to respond to queries, or responding incorrectly, causes both immediate Operational Problems and long term Problems with protocol development. This document identifies a number of common kinds of queries to which some servers either fail to respond or else respond incorrectly. This document also suggests procedures for zone operators to apply to identify and remediate the Problem. The document does not look at the DNS data itself, just the structure of the responses.

  • A Common Operational Problem in DNS Servers - Failure To Respond.
    2015
    Co-Authors: Mark Andrews
    Abstract:

    The DNS is a query / response protocol. Failure to respond or to respond correctly to queries causes both immediate Operational Problems and long term Problems with protocol development. This document identifies a number of common classes of queries to which some servers either fail to respond or else respond incorrectly. This document also suggests procedures for TLD and other similar zone operators to apply to help reduce / eliminate the Problem. The document does not look at the DNS data itself, just the structure of the responses.

Don Gelowitz - One of the best experts on this subject based on the ideXlab platform.

  • application of neuro fuzzy modeling technique for Operational Problem solving in a co2 capture process system
    International Journal of Greenhouse Gas Control, 2013
    Co-Authors: Qing Zhou, Christine W Chan, Paitoon Tontiwachwuthikul, Raphael Idem, Don Gelowitz
    Abstract:

    Abstract A good understanding about relationships among key process parameters is important in optimizing operation and enhancing efficiency of the CO 2 capture process system. This understanding would enable the operator to better analyze process conditions and become aware of ongoing trends or events so that timely and effective control actions can be taken for adjusting the relevant process parameters and efficiency of plant operations can be enhanced. The studies that focused on exploring the key parameters of the amine-based post-combustion CO 2 capture process system implemented at the International Test Center of CO 2 Capture (ITC) have revealed that among multiple data modeling techniques adopted, the adaptive-network-based fuzzy inference system (ANFIS) modeling approach generated satisfactory models for adequately describing the process system. This paper presents development and application of the four ANFIS models for solving four real-life Problems encountered in operation of the CO 2 capture process system. The testing results of the four developed models show that they can be applied for satisfactory solution of these Problems. Some lessons and observations made during the application process are also discussed.

  • application of three artificial intelligence techniques for Operational Problem solving in a co 2 capture process system
    International Workshop on Advanced Computational Intelligence, 2011
    Co-Authors: Qing Zhou, Christine W Chan, Paitoon Tontiwachwuthikul, Raphael Idem, Yuxiang Wu, Don Gelowitz
    Abstract:

    A good understanding of the key process parameters and their intricate relationships is critical for improving effectiveness and efficiency of the post combustion CO 2 capture process. The knowledge can help operators with prediction, control and decision-making. Although some critical parameters of the CO 2 capture process, such as reboiler heat duty, have been discussed in the previous research, their significances of influence and the nature of their relationships that affects efficiency of the CO 2 capture processes are not studied. This paper presents a study on exploring the key parameters of the amine-based post combustion CO 2 capture process system at the International Test Centre of CO 2 Capture (ITC) located in Regina, Saskatchewan of Canada. Three artificial intelligence (AI) techniques of sensitivity analysis (SA), artificial neural network (ANN), and neuro-fuzzy modeling were applied for modeling the historical data to identify the relationships among the key parameters. The knowledge obtained in this data modeling study can be useful for tackling the challenges in operation of the process system.