1,720,990 research outputs found
An efficient variable neighborhood search for solving a robust dynamic facility location problem in emergency service network
No full textIn this study, we propose a robust variant of a dynamic facility location problem that arises from optimizing the emergency service network of Police Special Forces Units (PSFUs) in the Republic of Serbia. We present for the first time a mathematical programming formulation of the problem under consideration. We further propose a Variable Neighborhood Search (VNS) method with an efficient local search procedure for solving real-life problem instances that remained out of reach of CPLEX solver. The results presented in this paper may help in optimizing the network of PSFUs and other security networks as well
Variable Neighborhood Search for Integrated Timetable Based Design of Railway Infrastructure
No full textIn this paper we deal with the problem of building new or extending an existing railway infrastructure. The goal is to determine a minimum cost infrastructure ful lling the requirements de ned by an integrated timetable and the operation of the railway system. We rst model this planning task as a combinatorial network optimization problem, capturing the essential aspects. We then present a metaheuristic solution method based on general variable neighborhood search that makes use of a dynamic programming procedure for realizing individual connections. Computational experiments indicate that the suggested approach is promising and the analysis of obtained results gives useful hints for future work in this area
Circular logistics and operations: transportation across a product’s lifecycle
No full textThe transition to the circular economy is underway but needs to overcome decades of linear thinking underpinning operations optimization and practices. The main difference between linear and circular operations is the role of consumers, from just recipients of finished goods to also being suppliers of cores (used products), which repair centers, remanufacturers, and other CE stakeholders can use as inputs to their operations. This transformation or change of roles underpins a huge increase of uncertainty, as supply is no longer limited in a mostly business-to-business-to-customer context, but rather customer-to-business-to-customer context, and has important ramifications on all operations, including transportation. With the goal being to eliminate materials reaching landfill, it is reasonable to expect that any forward (delivery) operation needs to be mirrored by a reverse (collection) operation, to close the loop and support circular logistics. This change is not trivial nor straightforward, as it is also not properly understood. To address this complex but crucial problem, this chapter proposes numerical analysis for designing a data-driven, operation-level decision-making support system that can dynamically allocate limited resources (e.g., transport capacity) to the right operations. We apply Monte Carlo simulation to consider pre-inspection, consolidation, and a product’s lifecycle for the chosen real-life case study. We employ forecasting to determine quality-based allocation across CE stakeholders (repair, remanufacturing, recycling) and consider various factors on a synthesized dataset, empirically grounded on data and discussions from and with experienced managers in the area. We find that pre-inspection and consolidation at the retailer is beneficial and that the benefits depend on the warranty duration relative to customer behavior (demand and return rates)
Real-Time Capacity Management and Patient Flow Optimization in Hospitals Using AI Methods
No full textHospital systems are under constant pressure to provide quality care despite limited resources. However, traditional capacity management in hospitals is often not effective enough. One reason for this is the variability and uncertainty in the healthcare field that has to be managed. Another reason is the observation that hospitals are open loop systems, meaning they do not use feedback to determine if their output has achieved the desired goal of input. They do not observe the output of their processes controlled by them and use this information to take action. In hospital systems, there are few efficient planning systems or decision support systems to help administrators take decisions. This is different in other industries, where complex planning systems with the help of Artificial Intelligence, or AI as it is referred to, are often being used. This research chapter analyses the issues and possibilities for hospitals to incorporate AI into their capacity management and become intelligent systems in which operations and processes are regulated by feedback (closed loop system) and, more specifically, discusses the recent research of the authors on this topic, where Artificial Intelligent (Multi-Agent System) methods in combination with real-time coordination were described and implemented in the Aravind Eye Hospital (AEH) in India
Solving the 3-Staged 2-Dimensional Cutting Stock Problem by Dynamic Programming and Variable Neighborhood Search
No full textWe present a variable neighborhood search (VNS) for the 3-st
aged 2-dimensional cutting stock problem employing "ruin-and-recreate"-based very large neighborhood search in which parts of the incumbent solution are destroyed and rebuilt using construction heuristics and dynamic programming. Experimental results show that
for instances where the sizes of the elements are not too small compared to the sheet size the hybridization of VNS with dynamic programming significantly outperforms a VNS relying solely on construction heuristics
Boosting an exact logic-based benders decomposition approach by variable neighborhood search.
No full textLogic-based Benders decomposition (BD) extends classic BD by allowing more complex subproblems with integral variables. Metaheuristics like variable neighborhood search are becoming useful here for faster solving the subproblems' inference duals in order to separate approximate Benders cuts. After performing such a purely heuristic BD approach, we continue by exactly verifying and possibly correcting each heuristic cut to finally obtain a proven optimal solution. On a bi-level vehicle routing problem, this new hybrid approach exhibits shorter overall runtimes and yields excellent intermediate solutions much earlier than the classical exact method
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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