The increasing size and complexity of communication satellites has made the manual management of their payloads by engineers through computerised schematics difficult and error prone. This article proposes to optimise...
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ISBN:
(纸本)9783642284908
The increasing size and complexity of communication satellites has made the manual management of their payloads by engineers through computerised schematics difficult and error prone. This article proposes to optimise payload reconfigurations for current and next generation satellites using a novel integerlinearprogramming model (ILP), which is a variant of network flow models. Experimental results using CPLEX demonstrate the efficiency and scalability of the approach up to realistic satellite payloads sizes and configurations.
Sudden service disruption due to natural or man-made disaster is one of the major threats to commercial supply chains and military logistics at present. In this paper, we present an integer-linear programming model fo...
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ISBN:
(纸本)9780769538044
Sudden service disruption due to natural or man-made disaster is one of the major threats to commercial supply chains and military logistics at present. In this paper, we present an integer-linear programming model for critical facilities protection based on time satisfaction, which could overcome the weakness of simply using time and distance in previous researches. The objective function is maximizing time satisfaction of the system in every elimination pattern. Then we combine genetic algorithms (GAs) with simulated annealing to solve this model. At the end, a numerical example is used to illustrate the application of the model, which shows the method is feasible and efficient.
This paper focuses on a dynamic embedding of client-constrained heterogeneous Virtual Network (VN) requests with multiple nodes and links affinity and anti-affinity requirements. For this Virtual Network Embedding (VN...
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ISBN:
(纸本)9798350300741;9798350300734
This paper focuses on a dynamic embedding of client-constrained heterogeneous Virtual Network (VN) requests with multiple nodes and links affinity and anti-affinity requirements. For this Virtual Network Embedding (VNE) problem, we formulate an integer-linear programming (ILP)-based model that achieves joint mapping of virtual nodes and links of each VN onto the dynamically updated Substrate Network (SN). This model not only meets the clients expressed isolation constraints but also includes VN request arrivals and departures to update SN information. Numerical experiments illustrate the efficiency of the proposed methods and their ability to find optimal solutions. Performance reports provide cloud service providers with insights into additional investments in nodes and links they should make to serve clients with anti-affinity requirements.
The possibilities of enabling travelers to walk a short distance to reach their prescribed pickup locations or final destinations in ridesharing services have received a lot of attention in recent years. This thesis c...
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The possibilities of enabling travelers to walk a short distance to reach their prescribed pickup locations or final destinations in ridesharing services have received a lot of attention in recent years. This thesis classifies the existing literature on ridesharing with walking trip legs into three different classes. Additionally, this thesis presents a variant of the single-vehicle pickup and delivery problem with time windows (PDPTW), called the pickup and delivery problem with time windows and walking legs (PDPTWWL), that explicitly incorporates the access and egress walking trips of travelers into the decision space. The proposed model targets a ridesharing service that can pool together two to three requests, and it is solved to optimality using a commercial mixed integerprogramming (MIP) solver. The candidate pickup/drop-off (PUDO) locations for each request are either the road intersections or street centerline midpoints within a pre-defined maximum allowable walking time. The study applies the model to two road network datasets—Isla Vista and Chicago downtown—reflecting different real-world application scenarios, and it presents various performance metrics based on a large number of randomly generated 2-request, 3-request, and 4-requesst PDPTWWL instances. The results indicate that a relatively short allowable walking time has a comparatively high vehicle driving time reduction per second of walking (DTRPSW) relative to a long allowable walking time. Moreover, pooling a larger number of requests (e.g., four requests) in one vehicle can lead to a much larger reduction in vehicle driving time and a higher DTRPSW, compared to pooling only two requests in one vehicle.
Most knowledge-intensive industries, especially companies developing software engineering projects such as Enterprise Resource Planning (ERP) implementation projects, generally necessitate finding the optimal trade-of...
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Most knowledge-intensive industries, especially companies developing software engineering projects such as Enterprise Resource Planning (ERP) implementation projects, generally necessitate finding the optimal trade-off between the project duration and total usage cost of the renewable resource costs (e.g., human resource expertise costs). Therefore, the MRC-DTCTP, which integrates classical multi-mode resource-constrained project scheduling (MRCPSP) and discrete time-cost trade-off problems (DTCTP), can be seen as a more applicable problem since it better reflects the objectives and requirements of today's real-life software project applications. The MRC-DTCTP is a much more complex variant of the MRCPSP since it aims to minimize total direct/indirect costs of the resources simultaneously under a pre-specified project deadline. Based on this motivation, a new explicit integer-linear programming (ILP) model of the MRC-DTCTP was first developed based on the implicit non-linearprogramming model of Wuliang and Chengen (2009). Due to its NP-hard nature, we also proposed a constraint programming (CP) model that includes several search strategies to solve large-sized problem instances within reasonable computation time. In addition, a genetic algorithm (GA) approach in combination with a Modified Serial Schedule Generation scheme (SSGS) is implemented to make further comparisons on several benchmark instances, which are generated based on the existing MRCPSP data sets taken from the project scheduling problem library (PSPLIB) by considering additional problem characteristics. A comprehensive experimental study has shown that the proposed CP model and GA approach can provide superior results in shorter run times for large-sized benchmark instances. Finally, an international Enterprise Resource Planning (ERP) Software Company's real-life application is presented. The ERP projects generally necessitate finding the optimal trade-off between project makespan and human resource
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