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EXPERIMENTAL MATHEMATICS 2024年第2期33卷 175-192页

作者： Fischer, Greta Gutt, Jean Junger, Michael Univ Cologne Dept Math & Comp Sci Cologne Germany Univ Toulouse Inst Math Toulouse France INU Champollion Albi France

In this article we explore a symplectic packing problem where the targets and domains are 2n-dimensional symplectic manifolds. We work in the context where the manifolds have first homology group equal to Z(n) , and we require the embeddings to induce isomorphisms between first homology groups. In this case, Miller Maley, Mastrangeli, and Traynor showed that the problem can be reduced to a combinatorial optimization problem, namely packing certain allowable simplices into a given standard simplex. They designed a computer program and presented computational results. In particular, they determined the simplex packing widths in dimension four for up to k = 12 simplices, along with lower bounds for higher values of k. We present a modified algorithmic approach that allows us to determine the k-simplex packing widths for up to k = 13 simplices in dimension four and up to k = 8 simplices in dimension six. Moreover, our approach determines all simplex-multisets that allow for optimal packings.

关键词： Symplectic packings symplectic capacities combinatorial optimization mixed integer linear programming semidefinite programming

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Freight-on-Transit for urban last-mile deliveries: A strategic planning approach

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TRANSPORTATION RESEARCH PART B-METHODOLOGICAL 2023年 169卷 53-81页

作者： Delle Donne, Diego Alfandari, Laurent Archetti, Claudia Ljubic, Ivana ESSEC Business Sch Dept Informat Syst Decis Sci & Stat Cergy France

We study a delivery strategy for last-mile deliveries in urban areas which combines freight transportation with mass mobility systems with the goal of creating synergies contrasting negative externalities caused by transportation. The idea is to use the residual capacity on public transport means for moving freight within the city. In particular, the system is such that parcels are first transported from origins (central distribution centers) to drop-in stations, which are stop locations on public vehicle itineraries. Then, they are transported on public vehicles to drop-out stations, from where they are delivered to destination by green vehicles (such as bikes, drones, porters, etc.). The system is known as Freight-On-Transit (FOT). In this paper, we focus on the strategic decisions related to defining the public transportation network that will take part in the delivery system, i.e., which public vehicle lines and stop locations will be included (and thus equipped for the service). We propose different formulations for the problem and effective heuristic solution approaches based on column generation. We perform exhaustive tests aimed at providing managerial insights on the performance and the efficiency of the system.

关键词： Freight-on-Transit Network flow Column generation mixed integer linear programming

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Data-driven optimization for automated warehouse operations decarbonization

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ANNALS OF OPERATIONS RESEARCH 2024年第3期343卷 1129-1156页

作者： Li, Haolin Wang, Shuaian Zhen, Lu Wang, Xiaofan Shanghai Univ Sch Management Shanghai Peoples R China Hong Kong Polytech Univ Dept Logist & Maritime Studies Hong Kong Peoples R China

The rapid development of intelligent warehouse systems is resulting in the realization of automation in warehouse activities and raising awareness of decarbonization, particularly the need to reduce carbon emissions from electricity consumption. Driven by the decarbonization trend, microgrid systems with rooftop photovoltaic panels are becoming more popular in warehouses and are providing zero-carbon electricity for warehouse operations. How to make better use of microgrid systems and reduce the consumption of electricity generated from traditional energy sources is becoming increasingly important in warehouse systems. This paper investigates an operational problem in a warehouse system equipped with a shuttle-based storage and retrieval system, in which a microgrid system acts as the main electricity source. Power-load management is applied to avoid peaks of energy consumption, and a mixed linear programming model is developed to optimize task sequencing and scheduling with decarbonization awareness. To solve the proposed problem, a data-driven variable neighbourhood search algorithm is built. Numerical experiments are conducted to validate the model and algorithm. Sensitivity analysis shows the effectiveness of power-load management and the influence of system configuration on energy consumption.

关键词： Automated warehouse Decarbonization Warehouse operations management mixed integer linear programming

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MPC-Based Black Start and Restoration for Resilient DER-Rich Electric Distribution System

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IEEE ACCESS 2023年 11卷 69177-69189页

作者： Konar, Srayashi Srivastava, Anurag K. Washington State Univ Sch Elect Engn & Comp Sci Pullman WA 99163 USA West Virginia Univ Dept Comp Sci & Elect Engn Morgantown WV 26506 USA

For past several years the resiliency of the power grid is severely challenged by extreme events. Black start and restoration scheme (BS & RS) is critical to enhance distribution grid resiliency. Variability in the power supply capacity of distributed energy resources (DERs) and load demand stand against the efficiency of sequential black start restoration of an unbalanced distribution system. An efficient black start restoration scheme must consider forecasted generation and demand profile to assess resource participation and generate valid switching sequence during sequential restoration of distribution grid. This work proposes a novel model predictive control (MPC) based efficient BS & RS strategy for reconfigurable distribution grid with DERs. The proposed algorithm generates optimal switching sequence by coordinating smart switches, black start DERs (BS-DERs) and energy storage systems (ESSs). Active power-frequency droop, reactive power-voltage droop and ramp rate constraints are assigned to BS-DERs for practical purposes. The non-convexity of sequential service restoration problem due to operational constraints of distribution grid, line switches and dynamics of ESS are linearized and solved as a mixed integer linear programming problem (MILP). The proposed scheme is also extended to incorporate errors associated with forecasting, DER capacity and load demand. Results of IEEE 123-bus and 1069-bus systems indicate effectiveness of the proposed approach.

关键词： Generators Power grids Switches Mathematical models Heuristic algorithms Resilience Distributed power generation mixed integer linear programming Active distribution grid black start restoration distributed energy resources resource coordination centralized optimization mixed integer problem

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Cov-trans: an efficient algorithm for discontinuous transcript assembly in coronaviruses

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BMC GENOMICS 2024年第1期25卷 1-11页

作者： Guo, Xiaoyu Wu, Zhenming Zhang, Shu Zhao, Jin Qingdao Univ Sch Comp Sci & Technol Ningxia Rd Qingdao 266071 Shandong Peoples R China

BackgroundDiscontinuous transcription allows coronaviruses to efficiently replicate and transmit within host cells, enhancing their adaptability and survival. Assembling viral transcripts is crucial for virology research and the development of antiviral strategies. However, traditional transcript assembly methods primarily designed for variable alternative splicing events in eukaryotes are not suitable for the viral transcript assembly problem. The current algorithms designed for assembling viral transcripts often struggle with low accuracy in determining the transcript boundaries. There is an urgent need to develop a highly accurate viral transcript assembly *** this work, we propose Cov-trans, a reference-based transcript assembler specifically tailored for the discontinuous transcription of coronaviruses. Cov-trans first identifies canonical transcripts based on discontinuous transcription mechanisms, start and stop codons, as well as reads alignment information. Subsequently, it formulates the assembly of non-canonical transcripts as a path extraction problem, and introduces a mixed integer linear programming to recover these non-canonical *** results show that Cov-trans outperforms other assemblers in both accuracy and recall, with a notable strength in accurately identifying the boundaries of transcripts. Cov-trans is freely available at https://***/computer-Bioinfo/***.

关键词： Referenced-based assembly mixed integer linear programming Discontinuous transcription Coronaviruses

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Optimizing the ecological connectivity of landscapes

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NETWORKS 2023年第2期81卷 278-293页

作者： Hamonic, Francois Albert, Cecile Couetoux, Basile Vaxes, Yann Aix Marseille Univ LIS CNRS Marseille France Aix Marseille Univ Univ Avignon IMBE CNRSIRD Marseille France

In this article, we consider the problem of optimizing the connectivity of a landscape under a budget constraint, by improving habitat areas and ecological corridors between them. We model this problem as a discrete optimization problem over graphs, in which vertices represent the habitat areas and arcs represent the connections between them. We propose a new flow-based integer linear programming formulation that improves upon the existing models for this problem. By following an approach similar to Catanzaro et al. for the robust shortest path problem, we design an improved preprocessing algorithm that reduces the size of the graphs on which we compute generalized flows. Computational experiments show the benefits of both contributions, by enabling to solve instances of the problem larger than previous models. These experiments also show that several versions of greedy algorithms perform relatively well in practice, while returning arbitrarily bad solutions in the worst case.

关键词： combinatorial optimization environment and climate change landscape connectivity mixed integer linear programming network flow shortest path

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A pragmatic optimization-based approach for analysis and configuration of a reconfigurable multi-product assembly line in the automotive industry

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INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY 2023年第9-10期129卷 3993-4010页

作者： Stief, Paul Burgat, Guillaume Pour-Massahian-Tafti, Meisam Dantan, Jean-Yves Siadat, Ali Univ Lorraine HESAM Univ Arts & Metiers Inst Technol LCFC F-57070 Metz France Thyssenkrupp Presta France SAS F-57192 Florange France

Increasing product variety and fluctuating demand have led to the need of assembly systems that can adapt to multiple different products as the return of investment for dedicated assembly lines is more and more difficult to achieve. In response to this challenge, the paradigm of reconfigurable assembly systems has emerged. However, configuring and optimizing these systems still pose challenges in the industry. This paper proposes a new simple optimization approach for the configuration analysis and optimization of a reconfigurable multi-product assembly system in the automotive industry, using configuration selection, task allocation, and sequencing. Its effectiveness is validated throughout three real industrial study cases in the automotive supplier industry.

关键词： Assembly system configuration Task-resource allocation Sequencing mixed integer linear programming Product variety

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An optimization model for sizing a concentrated solar power system with thermal energy storage

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ENERGY SYSTEMS-OPTIMIZATION MODELING SIMULATION AND ECONOMIC ASPECTS 2024年 1-25页

作者： Ghaithan, Ahmed M. King Fahd Univ Petr & Minerals Architectural Engn & Construct Management Dept Dhahran Saudi Arabia King Fahd Univ Petr & Minerals Ctr Smart Mobil & Logist Dhahran 31261 Saudi Arabia

This paper aims to develop a mixed integer linear programming model for optimal sizing of a concentrated solar power system with thermal energy storage. A case study is provided to demonstrate the utility and practicality of the developed model based on a residential area in Saudi Arabia. The optimal configuration comprises a solar field area of 146,013 square meters which will generate energy at 0.115 $/kWh. The renewable system demonstrates significant environmental benefits by reducing carbon dioxide emissions by more than 96% compared to the grid. The obtained results of the proposed system are validated by benchmarking against other systems in the literature. This research contributes to the field by providing a methodological approach for optimal sizing of renewable energy systems, addressing the critical issues of environmental impact and natural resources depletion.

关键词： Concentrated solar power mixed integer linear programming Optimal sizing Thermal energy storage

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A distributed object-oriented simulator framework for marine power plants with weak power grids

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JOURNAL OF MARINE ENGINEERING AND TECHNOLOGY 2023年第4期22卷 176-188页

作者： Skjong, Stian Pedersen, Eilif SINTEF Ocean Dept Fisheries & New Biomarine Ind Alesund Norway Norwegian Univ Sci & Technol Dept Marine Technol Trondheim Norway

In this work, we discuss and demonstrate how multi-engine marine power plants with weak power grids efficiently can be set up and simulated in a distributed co-simulation framework. To facilitate configuration switching such as starting and stopping, connecting and disconnecting arbitrary gensets online, the generator models are modelled as hybrid causality component models. This implementation enables seamless and energy conservative model switching. Also, the proposed simulator framework is scalable such that the number of gensets in the power plant can be set by a single parameter, which automatically scales the power management system and the tailored simulator master algorithm accordingly. To control the number of active gensets being connected to the power grid while running the simulation, a simple mixed integer linear programming formulation is proposed. A simulation case study including a marine power plant configuration with four equal-sized gensets is conducted in the end to demonstrate the features of the proposed simulator framework, which also can be applied to, e.g. a small wind farm, or an isolated number of islands with interconnected power generators.

关键词： Marine power plant Hybrid generator models Co-simulation Power management system mixed integer linear programming Power plant control

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Layout optimization of truss structures with modular constraints

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STRUCTURES 2023年 55卷 1460-1469页

作者： Liu, Yufeng Wang, Zhen Lu, Hongjia Ye, Jun Zhao, Yang Xie, Yi Min Zhejiang Univ Coll Civil Engn & Architecture Hangzhou 310058 Peoples R China Hangzhou City Univ Dept Civil Engn Hangzhou 310015 Peoples R China RMIT Univ Ctr Innovat Struct & Mat Sch Engn Melbourne 3001 Australia Shaoxing Univ Sch Civil Engn Shaoxing 312000 Peoples R China Zhejiang Univ Ctr Balance Architecture Hangzhou 310014 Peoples R China

Truss layout optimization is a well-established technique for designing efficient structures, but the optimized structures are often complex and associated with high manufacturing costs. To address this problem, repetitive modules are often used. However, relying solely on a single type of module may negatively impact the structural efficiency. To mitigate this trade-off, this study presents a novel approach for designing truss structures that incorporates multiple types of modules. Additionally, both the module arrangement and module structures are determined by the optimization approach. To achieve this, a novel mixed-integer linear programming problem is developed, and a heuristic method is proposed to enhance computational efficiency. The proposed approach is validated through several numerical examples, which demonstrate its ability to produce truss designs with low manufacturing costs and high structural efficiency.

关键词： Structure optimization Modular constraints Truss layout optimization mixed integer linear programming

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