The Experts below are selected from a list of 210 Experts worldwide ranked by ideXlab platform
Gündüz Ulusoy - One of the best experts on this subject based on the ideXlab platform.
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A combination of different Resource Management policies in a multi-project environment
2013Co-Authors: Umut Beşikci, Gündüz Ulusoy, Ümit BilgeAbstract:Multi-project problem environments are defined according to the way Resources are managed in the problem environment which is called the Resource Management Policy (RMP) in this study. Different Resource Management policies can be defined according to the characteristics of the projects and/or Resources in the problem environment. The most common RMP encountered in the multi-project scheduling literature is the Resource sharing Policy (RSP) where Resources can be shared among projects without any costs or limitations. This Policy can be seen as an extreme case since there is a strong assumption of unconstrained Resource sharing. Another RMP can be defined as the other extreme such that Resources cannot be shared among projects which is called Resource the dedication Policy (RDP). The last RMP considered in this study is between these two policies where Resources are dedicated but can be transferred among projects when a project finishes, the dedicated Resources to this project can be transferred to another one starting after the finish of the corresponding project. This RPM is called the Resource transfer Policy (RTP). In this study we investigate a problem environment where all these three types of RPM are present. Additionally, the general Resource capacities are taken as decision variables that are constrained by a given general budget. We call this multi-project environment as the Generalized Resource Portfolio Problem (GRPP). We have investigated this problem and proposed an iterative solution approach based on exact solution methods which determines the general Resource capacities from the budget, Resource dedications, Resource sharing and Resource transfer decisions and schedules the individual projects. Computational results for over forty test problems are reported.
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A modied branch and cut procedure for Resource portfolio problem under relaxed Resource dedication Policy
2012Co-Authors: Umut Beşikci, Ümit Bilge, Gündüz UlusoyAbstract:Multi-project scheduling problems are characterized by the way Resources are managed in the problem environment. The general approach in multi-project scheduling literature is to consider Resource capacities as a common pool that can be shared among all projects without any restrictions or costs. The way the Resources are used in a multi-project environment is called Resource Management Policy and the aforementioned assumption is called Resource Sharing Policy in this study. The Resource sharing Policy is not a generalization for multi-project scheduling environments and different Resource Management policies maybe defined to identify characteristics of different problem environments. In this study, we present a Resource Management Policy which prevents sharing of Resources among projects but allows Resource transfers when a project starts after the completion of another one. This Policy is called the Relaxed Resource Dedication (RRD) Policy in this study. The general Resource capacities might or might not be decision variables. We will treat here the case where the general available amounts of Resources are decision variables to be determined subject to a limited budget. We call this problem as the Resource Portfolio Problem (RPP). In this study, RPP is investigated under RRD Policy and a modified Branch and Cut (B&C)procedure based on CPLEX is proposed. The B&C procedure of CPLEX is modified with different branching strategies, heuristic solution approaches and valid inequalities. The computational studies presented demonstrate the effectiveness of the proposed solution approaches.
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Resource portfolio problem under relaxed Resource dedication Policy in a multi-project environment
2012Co-Authors: Umut Beşikci, Ümit Bilge, Gündüz UlusoyAbstract:The characterization of the way Resources are used by individual projects in the multi-project environment is called Resource Management Policy in this study. The common Resource usage approach in multi-project scheduling literature allows the sharing of Resources without any restrictions or costs among projects. An extension is proposed Kruger and Scholl (2009) and Kruger and Scholl (2010) which allows for Resource sharing with sequence dependent transfer times. Another Resource Management Policy called Resource dedication Policy is proposed by Besikci et al. (2011) and further investigated in Besikci et al. (2012), where Resources cannot be shared among the projects and must be dedicated. According to the characteristics of Resources and projects, Resource dedication Policy can be extended to relaxed Resource dedication Policy where the renewable Resources dedicated to a particular project can be transferred after that project's nish time to other projects that are yet to start. In some multi-project environments, the Resource availability values can be considered as another set of decisions, which can be thought as a higher decision level, resulting in general Resource capacities. This problem is de ned as the Resource portfolio problem and can be modeled in di erent forms based on the particular Resource Management Policy. Here, we will deal with the Resource portfolio problem under relaxed Resource dedication (RPP-RRD) Policy.
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Different Resource Management Policies in Multi-Mode Resource Constrained Multi-Project Scheduling
2011Co-Authors: Umut Beşikci, Ümit Bilge, Gündüz UlusoyAbstract:This study investigates different Resource Management policies in Resource constrained multi-project problem environments. The problem environment under investigation has alternative modes for activities, a set of renewable and nonrenewable Resources used by activities and further considerations such as general Resource budget. The characterization of the way Resources are used by individual projects in the multiproject environment is called Resource Management Policy in this study. The solution approaches in the literature for multi-project problems generally defines the Resources as a pool that can be shared by all the projects which in fact creates a general assumption for the Resource usage characteristics. This Resource Management Policy is referred as Resource sharing Policy in this study. Resource sharing Policy can be invalid in some certain cases where sharing assumption is not feasible because of some characteristics of Resources and/or projects which require different Resource Management policies for the multi-project environment. According to the characteristics of Resources and projects, Resource Management policies such as Resource dedication, relaxed Resource dedication and generalized Resource Management policies can be defined. In this paper, these Resource Management policies will be defined and their mathematical formulations will be presented and discussed.
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Resource preference based improvement heuristics for Resource portfolioproblem
2011Co-Authors: Umut Beşikci, Ümit Bilge, Gündüz UlusoyAbstract:The multi-project problem environment under consideration involves multiple-projects with activities having alternative execution modes, a general Resource budget and a Resource Management Policy that does not allow sharing of Resources among projects. The multi-project scheduling model for this problem environment is called Resource Portfolio Problem. There are three basic conceptual problems in RPP: (i) determining the general Resource capacities from the given general Resource budget (general Resource capacities determination); (ii) dedication of the general Resource capacities to projects (Resource dedication) and finally (iii) scheduling of individual projects with the given Resource dedications. In this study, different preference based improvement heuristics are proposed for general Resource capacities determination and Resource dedication conceptual problems. For general Resource capacities determination, the current general Resource capacity values are changed according to the Resource preferences such that the resulting capacity state would be more preferable. Similarly for Resource dedication, Resource dedication values of projects are changed according to the preferences of projects for Resources such that the resulting Resource dedication state would be more preferable. These two improvement heuristics separates and couples the conceptual problems. Different preference calculation methods are proposed employing Lagrangian relaxation and linear relaxation of MRCPSP formulation.
Ali Kharrazi - One of the best experts on this subject based on the ideXlab platform.
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evaluating the evolution of the heihe river basin using the ecological network analysis efficiency resilience and implications for water Resource Management Policy
Science of The Total Environment, 2016Co-Authors: Ali Kharrazi, Yadong Yu, Jia LiAbstract:One of the most critical challenges in the anthropocentric age is the sustainable Management of the planet's increasingly strained water Resources. In this avenue, there is a need to advance holistic approaches and objective tools which allow Policy makers to better evaluate system-level properties and trade-offs of water Resources. This research contributes to the expanding literature in this area by examining the changes to system-level network configurations of the middle reaches of the Heihe River basin from 2000 to 2009. Specifically, through the ecological network analysis (ENA) approach, this research examines changes to the system-level properties of efficiency, redundancy, and evaluates the trade-offs to the resiliency of ecosystem water services of the middle reaches of the Heihe River basin. Our results indicate that while the efficiency of the middle reaches has increased from 2000 to 2009 by 6% and 78% more water is released to the lower reaches, the redundancy of the system has also decreased by 6%. The lower level of redundancy, particularly due to the changes in the groundwater body levels, has critical long-term consequences for the resilience of the water ecosystem services of the middle reaches. In consideration of these holistic trade-offs, two hypothetical alternative scenarios, based on water recycling and saving strategies, are developed to improve the long-term health and resilience of the water system.
Umut Beşikci - One of the best experts on this subject based on the ideXlab platform.
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A combination of different Resource Management policies in a multi-project environment
2013Co-Authors: Umut Beşikci, Gündüz Ulusoy, Ümit BilgeAbstract:Multi-project problem environments are defined according to the way Resources are managed in the problem environment which is called the Resource Management Policy (RMP) in this study. Different Resource Management policies can be defined according to the characteristics of the projects and/or Resources in the problem environment. The most common RMP encountered in the multi-project scheduling literature is the Resource sharing Policy (RSP) where Resources can be shared among projects without any costs or limitations. This Policy can be seen as an extreme case since there is a strong assumption of unconstrained Resource sharing. Another RMP can be defined as the other extreme such that Resources cannot be shared among projects which is called Resource the dedication Policy (RDP). The last RMP considered in this study is between these two policies where Resources are dedicated but can be transferred among projects when a project finishes, the dedicated Resources to this project can be transferred to another one starting after the finish of the corresponding project. This RPM is called the Resource transfer Policy (RTP). In this study we investigate a problem environment where all these three types of RPM are present. Additionally, the general Resource capacities are taken as decision variables that are constrained by a given general budget. We call this multi-project environment as the Generalized Resource Portfolio Problem (GRPP). We have investigated this problem and proposed an iterative solution approach based on exact solution methods which determines the general Resource capacities from the budget, Resource dedications, Resource sharing and Resource transfer decisions and schedules the individual projects. Computational results for over forty test problems are reported.
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A modied branch and cut procedure for Resource portfolio problem under relaxed Resource dedication Policy
2012Co-Authors: Umut Beşikci, Ümit Bilge, Gündüz UlusoyAbstract:Multi-project scheduling problems are characterized by the way Resources are managed in the problem environment. The general approach in multi-project scheduling literature is to consider Resource capacities as a common pool that can be shared among all projects without any restrictions or costs. The way the Resources are used in a multi-project environment is called Resource Management Policy and the aforementioned assumption is called Resource Sharing Policy in this study. The Resource sharing Policy is not a generalization for multi-project scheduling environments and different Resource Management policies maybe defined to identify characteristics of different problem environments. In this study, we present a Resource Management Policy which prevents sharing of Resources among projects but allows Resource transfers when a project starts after the completion of another one. This Policy is called the Relaxed Resource Dedication (RRD) Policy in this study. The general Resource capacities might or might not be decision variables. We will treat here the case where the general available amounts of Resources are decision variables to be determined subject to a limited budget. We call this problem as the Resource Portfolio Problem (RPP). In this study, RPP is investigated under RRD Policy and a modified Branch and Cut (B&C)procedure based on CPLEX is proposed. The B&C procedure of CPLEX is modified with different branching strategies, heuristic solution approaches and valid inequalities. The computational studies presented demonstrate the effectiveness of the proposed solution approaches.
-
Resource portfolio problem under relaxed Resource dedication Policy in a multi-project environment
2012Co-Authors: Umut Beşikci, Ümit Bilge, Gündüz UlusoyAbstract:The characterization of the way Resources are used by individual projects in the multi-project environment is called Resource Management Policy in this study. The common Resource usage approach in multi-project scheduling literature allows the sharing of Resources without any restrictions or costs among projects. An extension is proposed Kruger and Scholl (2009) and Kruger and Scholl (2010) which allows for Resource sharing with sequence dependent transfer times. Another Resource Management Policy called Resource dedication Policy is proposed by Besikci et al. (2011) and further investigated in Besikci et al. (2012), where Resources cannot be shared among the projects and must be dedicated. According to the characteristics of Resources and projects, Resource dedication Policy can be extended to relaxed Resource dedication Policy where the renewable Resources dedicated to a particular project can be transferred after that project's nish time to other projects that are yet to start. In some multi-project environments, the Resource availability values can be considered as another set of decisions, which can be thought as a higher decision level, resulting in general Resource capacities. This problem is de ned as the Resource portfolio problem and can be modeled in di erent forms based on the particular Resource Management Policy. Here, we will deal with the Resource portfolio problem under relaxed Resource dedication (RPP-RRD) Policy.
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Different Resource Management Policies in Multi-Mode Resource Constrained Multi-Project Scheduling
2011Co-Authors: Umut Beşikci, Ümit Bilge, Gündüz UlusoyAbstract:This study investigates different Resource Management policies in Resource constrained multi-project problem environments. The problem environment under investigation has alternative modes for activities, a set of renewable and nonrenewable Resources used by activities and further considerations such as general Resource budget. The characterization of the way Resources are used by individual projects in the multiproject environment is called Resource Management Policy in this study. The solution approaches in the literature for multi-project problems generally defines the Resources as a pool that can be shared by all the projects which in fact creates a general assumption for the Resource usage characteristics. This Resource Management Policy is referred as Resource sharing Policy in this study. Resource sharing Policy can be invalid in some certain cases where sharing assumption is not feasible because of some characteristics of Resources and/or projects which require different Resource Management policies for the multi-project environment. According to the characteristics of Resources and projects, Resource Management policies such as Resource dedication, relaxed Resource dedication and generalized Resource Management policies can be defined. In this paper, these Resource Management policies will be defined and their mathematical formulations will be presented and discussed.
-
Resource preference based improvement heuristics for Resource portfolioproblem
2011Co-Authors: Umut Beşikci, Ümit Bilge, Gündüz UlusoyAbstract:The multi-project problem environment under consideration involves multiple-projects with activities having alternative execution modes, a general Resource budget and a Resource Management Policy that does not allow sharing of Resources among projects. The multi-project scheduling model for this problem environment is called Resource Portfolio Problem. There are three basic conceptual problems in RPP: (i) determining the general Resource capacities from the given general Resource budget (general Resource capacities determination); (ii) dedication of the general Resource capacities to projects (Resource dedication) and finally (iii) scheduling of individual projects with the given Resource dedications. In this study, different preference based improvement heuristics are proposed for general Resource capacities determination and Resource dedication conceptual problems. For general Resource capacities determination, the current general Resource capacity values are changed according to the Resource preferences such that the resulting capacity state would be more preferable. Similarly for Resource dedication, Resource dedication values of projects are changed according to the preferences of projects for Resources such that the resulting Resource dedication state would be more preferable. These two improvement heuristics separates and couples the conceptual problems. Different preference calculation methods are proposed employing Lagrangian relaxation and linear relaxation of MRCPSP formulation.
Ümit Bilge - One of the best experts on this subject based on the ideXlab platform.
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A combination of different Resource Management policies in a multi-project environment
2013Co-Authors: Umut Beşikci, Gündüz Ulusoy, Ümit BilgeAbstract:Multi-project problem environments are defined according to the way Resources are managed in the problem environment which is called the Resource Management Policy (RMP) in this study. Different Resource Management policies can be defined according to the characteristics of the projects and/or Resources in the problem environment. The most common RMP encountered in the multi-project scheduling literature is the Resource sharing Policy (RSP) where Resources can be shared among projects without any costs or limitations. This Policy can be seen as an extreme case since there is a strong assumption of unconstrained Resource sharing. Another RMP can be defined as the other extreme such that Resources cannot be shared among projects which is called Resource the dedication Policy (RDP). The last RMP considered in this study is between these two policies where Resources are dedicated but can be transferred among projects when a project finishes, the dedicated Resources to this project can be transferred to another one starting after the finish of the corresponding project. This RPM is called the Resource transfer Policy (RTP). In this study we investigate a problem environment where all these three types of RPM are present. Additionally, the general Resource capacities are taken as decision variables that are constrained by a given general budget. We call this multi-project environment as the Generalized Resource Portfolio Problem (GRPP). We have investigated this problem and proposed an iterative solution approach based on exact solution methods which determines the general Resource capacities from the budget, Resource dedications, Resource sharing and Resource transfer decisions and schedules the individual projects. Computational results for over forty test problems are reported.
-
A modied branch and cut procedure for Resource portfolio problem under relaxed Resource dedication Policy
2012Co-Authors: Umut Beşikci, Ümit Bilge, Gündüz UlusoyAbstract:Multi-project scheduling problems are characterized by the way Resources are managed in the problem environment. The general approach in multi-project scheduling literature is to consider Resource capacities as a common pool that can be shared among all projects without any restrictions or costs. The way the Resources are used in a multi-project environment is called Resource Management Policy and the aforementioned assumption is called Resource Sharing Policy in this study. The Resource sharing Policy is not a generalization for multi-project scheduling environments and different Resource Management policies maybe defined to identify characteristics of different problem environments. In this study, we present a Resource Management Policy which prevents sharing of Resources among projects but allows Resource transfers when a project starts after the completion of another one. This Policy is called the Relaxed Resource Dedication (RRD) Policy in this study. The general Resource capacities might or might not be decision variables. We will treat here the case where the general available amounts of Resources are decision variables to be determined subject to a limited budget. We call this problem as the Resource Portfolio Problem (RPP). In this study, RPP is investigated under RRD Policy and a modified Branch and Cut (B&C)procedure based on CPLEX is proposed. The B&C procedure of CPLEX is modified with different branching strategies, heuristic solution approaches and valid inequalities. The computational studies presented demonstrate the effectiveness of the proposed solution approaches.
-
Resource portfolio problem under relaxed Resource dedication Policy in a multi-project environment
2012Co-Authors: Umut Beşikci, Ümit Bilge, Gündüz UlusoyAbstract:The characterization of the way Resources are used by individual projects in the multi-project environment is called Resource Management Policy in this study. The common Resource usage approach in multi-project scheduling literature allows the sharing of Resources without any restrictions or costs among projects. An extension is proposed Kruger and Scholl (2009) and Kruger and Scholl (2010) which allows for Resource sharing with sequence dependent transfer times. Another Resource Management Policy called Resource dedication Policy is proposed by Besikci et al. (2011) and further investigated in Besikci et al. (2012), where Resources cannot be shared among the projects and must be dedicated. According to the characteristics of Resources and projects, Resource dedication Policy can be extended to relaxed Resource dedication Policy where the renewable Resources dedicated to a particular project can be transferred after that project's nish time to other projects that are yet to start. In some multi-project environments, the Resource availability values can be considered as another set of decisions, which can be thought as a higher decision level, resulting in general Resource capacities. This problem is de ned as the Resource portfolio problem and can be modeled in di erent forms based on the particular Resource Management Policy. Here, we will deal with the Resource portfolio problem under relaxed Resource dedication (RPP-RRD) Policy.
-
Different Resource Management Policies in Multi-Mode Resource Constrained Multi-Project Scheduling
2011Co-Authors: Umut Beşikci, Ümit Bilge, Gündüz UlusoyAbstract:This study investigates different Resource Management policies in Resource constrained multi-project problem environments. The problem environment under investigation has alternative modes for activities, a set of renewable and nonrenewable Resources used by activities and further considerations such as general Resource budget. The characterization of the way Resources are used by individual projects in the multiproject environment is called Resource Management Policy in this study. The solution approaches in the literature for multi-project problems generally defines the Resources as a pool that can be shared by all the projects which in fact creates a general assumption for the Resource usage characteristics. This Resource Management Policy is referred as Resource sharing Policy in this study. Resource sharing Policy can be invalid in some certain cases where sharing assumption is not feasible because of some characteristics of Resources and/or projects which require different Resource Management policies for the multi-project environment. According to the characteristics of Resources and projects, Resource Management policies such as Resource dedication, relaxed Resource dedication and generalized Resource Management policies can be defined. In this paper, these Resource Management policies will be defined and their mathematical formulations will be presented and discussed.
-
Resource preference based improvement heuristics for Resource portfolioproblem
2011Co-Authors: Umut Beşikci, Ümit Bilge, Gündüz UlusoyAbstract:The multi-project problem environment under consideration involves multiple-projects with activities having alternative execution modes, a general Resource budget and a Resource Management Policy that does not allow sharing of Resources among projects. The multi-project scheduling model for this problem environment is called Resource Portfolio Problem. There are three basic conceptual problems in RPP: (i) determining the general Resource capacities from the given general Resource budget (general Resource capacities determination); (ii) dedication of the general Resource capacities to projects (Resource dedication) and finally (iii) scheduling of individual projects with the given Resource dedications. In this study, different preference based improvement heuristics are proposed for general Resource capacities determination and Resource dedication conceptual problems. For general Resource capacities determination, the current general Resource capacity values are changed according to the Resource preferences such that the resulting capacity state would be more preferable. Similarly for Resource dedication, Resource dedication values of projects are changed according to the preferences of projects for Resources such that the resulting Resource dedication state would be more preferable. These two improvement heuristics separates and couples the conceptual problems. Different preference calculation methods are proposed employing Lagrangian relaxation and linear relaxation of MRCPSP formulation.
Jia Li - One of the best experts on this subject based on the ideXlab platform.
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evaluating the evolution of the heihe river basin using the ecological network analysis efficiency resilience and implications for water Resource Management Policy
Science of The Total Environment, 2016Co-Authors: Ali Kharrazi, Yadong Yu, Jia LiAbstract:One of the most critical challenges in the anthropocentric age is the sustainable Management of the planet's increasingly strained water Resources. In this avenue, there is a need to advance holistic approaches and objective tools which allow Policy makers to better evaluate system-level properties and trade-offs of water Resources. This research contributes to the expanding literature in this area by examining the changes to system-level network configurations of the middle reaches of the Heihe River basin from 2000 to 2009. Specifically, through the ecological network analysis (ENA) approach, this research examines changes to the system-level properties of efficiency, redundancy, and evaluates the trade-offs to the resiliency of ecosystem water services of the middle reaches of the Heihe River basin. Our results indicate that while the efficiency of the middle reaches has increased from 2000 to 2009 by 6% and 78% more water is released to the lower reaches, the redundancy of the system has also decreased by 6%. The lower level of redundancy, particularly due to the changes in the groundwater body levels, has critical long-term consequences for the resilience of the water ecosystem services of the middle reaches. In consideration of these holistic trade-offs, two hypothetical alternative scenarios, based on water recycling and saving strategies, are developed to improve the long-term health and resilience of the water system.
