In this article, we propose a highly reliable transmission strategy based on exploiting channel diversity for Internet of Things (IoT) networks equipped with cognitive radio (CR) capabilities (referred to as CR-IoT ne...
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In this article, we propose a highly reliable transmission strategy based on exploiting channel diversity for Internet of Things (IoT) networks equipped with cognitive radio (CR) capabilities (referred to as CR-IoT networks). Specifically, we investigate the channel-assignment problem with the objective of minimizing the number of assigned channels for each CR transmission subject to link reliability, data rate, and success probability constraints. We use the theory of continuous-time Markov chains to derive mathematical expressions for channel availability and reliability. These expressions are employed in a binary linear program model to formulate the channel assignment optimization problem, which is suboptimally solved using a polynomial-time sequential fixing procedure. Theoretical performance analysis of the proposed channel assignment scheme is derived in terms of a lower bound on the achievable probability of successful packet transmission. Through simulation experiments, we demonstrate significant performance enhancement compared to existing reliability-unaware CR channel assignment algorithms.
Existing methods for nonlinear robust control often use scenario-based approaches to formulate the control problem as nonlinear optimization problems. Increasing the number of scenarios improves robustness, while incr...
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ISBN:
(纸本)9781713872344
Existing methods for nonlinear robust control often use scenario-based approaches to formulate the control problem as nonlinear optimization problems. Increasing the number of scenarios improves robustness, while increasing the size of the optimization problems. Mitigating the size of the problem by reducing the number of scenarios requires knowledge about how the uncertainty affects the system. This paper draws from local reduction methods used in semi-infinite optimization to solve robust optimal control problems with parametric uncertainty. We show that nonlinear robust optimal control problems are equivalent to semi-infinite optimization problems and can be solved by local reduction. By iteratively adding interim globally worst-case scenarios to the problem, methods based on local reduction provide a way to manage the total number of scenarios. In particular, we show that local reduction methods find worst case scenarios that are not on the boundary of the uncertainty set. The proposed approach is illustrated with a case study with both parametric and additive time-varying uncertainty. The number of scenarios obtained from local reduction is 101, smaller than in the case when all 2(14+3x192) boundary scenarios are considered. A validation with randomly drawn scenarios shows that our proposed approach reduces the number of scenarios and ensures robustness even if local solvers are used. Copyright (C) 2023 The Authors.
Within the framework of second-order cone programming optimized micropolar continuum finite-element method (CosFEM-SOCP), the geotechnical strain localization can be adequately modeled. In most existing literatures, h...
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Within the framework of second-order cone programming optimized micropolar continuum finite-element method (CosFEM-SOCP), the geotechnical strain localization can be adequately modeled. In most existing literatures, however, the constant internal characteristic length l(c) has been adopted and less attention has been paid to the evolution of l(c). To more accurately predict the strain localization, response, and stability of a geotechnical system, one relationship for evolving l(v) that relies on the equivalent plastic strain is implemented and investigated. Based on one homogeneous slope example and one rigid strip footing example, it was found that geotechnical stability may not be significantly affected by evolving l(v), indicating that constant l(c) can be simply applied to geotechnical stability analysis. For the rigid strip footing problem, nevertheless, the effects of evolving l(v) on the pressure-displacement response curves should not be ignored, and the influence range of the shear band predicted by CosFEM-SOCP with evolving l(v) is generally smaller than that predicted by CosFEM-SOCP with constant l(c). Consequently, in order to more accurately predict the pressure-displacement response curves and the failure zone, the evolving l(v) will be adequately assessed and modeled.
Mimicking the biological visual attention mechanism to detect salient objects in images has been widely studied in recent years. Most of the existing computational models rely on external learning for saliency predict...
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Mimicking the biological visual attention mechanism to detect salient objects in images has been widely studied in recent years. Most of the existing computational models rely on external learning for saliency prediction, which however lack robustness in diversified scenes. In this paper, an unsupervised learning model is proposed to detect salient objects by fully exploiting the internal information of the scene. Specifically, we formulate saliency detection as a mathematical programming problem with which to learn a nonlinear feature mapping from multi-view features to saliency scores. The optimization objective is to maximize the between-class variance of the attended and background regions in the resulting saliency maps, which is statistically optimal. Moreover, to solve the non-convex constrained mathematical programming problem, a hybrid external point method based particle swarm optimization algorithm is developed to find the optimal solution in a rapid manner. Finally, extensive experiments are conducted on four classical saliency benchmark datasets to test the effectiveness of the proposed method and it shows superior qualitative and quantitative performance than the other 16 state-of-the-art unsupervised saliency models.
Cross-docking is a logistics process in which products are unloaded through receiving docks and then transferred to shipping docks with almost no storage in between. In this paper, a mixed integer linear programming m...
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Cross-docking is a logistics process in which products are unloaded through receiving docks and then transferred to shipping docks with almost no storage in between. In this paper, a mixed integer linear programming model (MILP) is proposed to optimise the scheduling, storage, assignment and sequencing of trucks at receiving and shipping docks for a problem inspired from a multiple-door cross-dock facility of an industrial partner with multiple temporary storage zones. The multiple storage zones are separated and located in the centre of the cross-dock handling different types of products. The objective is to minimise the total tardiness of inbound and outbound trucks. A heuristic (H) is proposed to find an initial solution. Then, three meta-heuristics are developed, namely Random Search (RS), Tabu Search (TS) and Simulated Annealing (SA) to improve the scheduling of trucks in order to minimise the tardiness of inbound and outbound trucks. Experimental results indicate that the three meta-heuristics (RS, TS and SA) are able to find good quality results within reasonable computational times. Finally, since SA showed the best performance compared to RS and TS, it was chosen to be compared to the current manual method using discrete event simulation.
Purpose The study has two main objectives. The first is to introduce three new examination policy practices: overbooked exam rooms, a substitute invigilator and an inheritance of the invigilation distribution. The sec...
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Purpose The study has two main objectives. The first is to introduce three new examination policy practices: overbooked exam rooms, a substitute invigilator and an inheritance of the invigilation distribution. The second is the use of the examination model to determine the sustainability of the system against expected changes and to obtain long-term strategic information. This study aims to obtain managerial insights on the sustainability of the examination system with the newly introduced practices;it does not claim to propose solutions for large-scale problems. Design/methodology/approach This study introduces a multi-objective mathematical model that contains a couple of constraints that belong to new practices. To check the sustainability of the system, this study gets help from sensitivity analysis, which informs the decision-maker about how the results will react to parameter changes. The authors perform all experiments in the Python/Gurobi modeling environment. Findings The results demonstrate that the proposed practices are effective in the efficient use of resources. Also, this study shows that the examination model can be used as a stress test so that the weaknesses of the system can be identified and long-term strategic information can be obtained. Originality/value The contribution of this study is twofold: the introduction of examination policy practices that are overbooked exam rooms, a substitute invigilator and an inheritance of the invigilation distribution. Overbooked exam rooms aim to use resources effectively, taking into account the possibility of temporarily increasing the exam room capacity. The substitute invigilator protects the examination process against sudden events. The inheritance of the invigilation distribution helps to ensure fairness;and the use of the examination model to obtain managerial insights on expectations. This allows testing the validity of existing policies and making necessary changes, taking into account possible chan
Effective computational methods are important for practitioners and researchers working in strategic underground mine planning. We consider a class of problems that can be modeled as a resource-constrained project sch...
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Effective computational methods are important for practitioners and researchers working in strategic underground mine planning. We consider a class of problems that can be modeled as a resource-constrained project scheduling problem with optional activities;the objective maximizes net present value. We provide a computational review of math programming and constraint programming techniques for this problem, describe and implement novel problem-size reductions, and introduce an aggregated linear program that guides a list scheduling algorithm running over unaggregated instances. Practical, large-scale planning problems cannot be processed using standard optimization approaches. However, our strategies allow us to solve them to within about 5% of optimality in several hours, even for the most difficult instances.
Data analysis workflows are popular for sequencing activities in large-scale and complex scientific processes. Scheduling approaches attempt to find an appropriate assignment of workflow tasks to the computing nodes f...
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Network slicing is an important characteristic of 5G/6G networks that increases flexibility and enables different applications over a single infrastructure. The physical resources are partitioned to create virtualized...
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ISBN:
(纸本)9798350399806
Network slicing is an important characteristic of 5G/6G networks that increases flexibility and enables different applications over a single infrastructure. The physical resources are partitioned to create virtualized networks, each dedicated to services with specific requirements. Several entities participate in network slicing, including Mobile Network Operators (MNOs), Mobile Virtual Network Operators (MVNOs), and users. An MNO owns the physical network infrastructure and the resources. MVNOs lease resources from the MNO and operate as service providers towards their subscribers. The goal of this work is to optimize the end-to-end network slicing process to provide services to users with a fair sharing of resources. We model this problem as a hierarchical combinatorial auction with a modified Vickrey-Clarke-Groves pricing mechanism. In the upper-level auction, an MNO is the seller supplying Network Slice to several MVNOs, who act as the bidders. In the lower-level auction, each MVNO holds an auction as a seller delivering services to their subscribed end-users, who play the role of bidders. We formulate and solve theWinner Determination Problem using mathematical programming and heuristic algorithms. The simulations show that the model can achieve fair sharing of resources, and it enables improving the MNO and MVNO revenue.
We consider the problem of deriving parameters of the preference model employed in the multiple criteria sorting method called Flow-Sort. We propose a suite of preference learning algorithms based on differential evol...
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ISBN:
(纸本)9798400701207
We consider the problem of deriving parameters of the preference model employed in the multiple criteria sorting method called Flow-Sort. We propose a suite of preference learning algorithms based on differential evolution and simulated annealing, their combinations with mathematical programming, and a dedicated heuristic. They are tested on various monotonic benchmark datasets and compared in terms of 0/1 loss. The evolutionary algorithm and the dedicated heuristic prove competitive against state-of-the-art preference learning methods. The former attains better results when coupled with boundary profiles for all considered datasets. For other methods, there is no clear indication that using the class limits is more advantageous than class prototypes.
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