Search results for "Abstract"
showing 10 items of 1959 documents
Novel Distance Estimation Methods Using 'Stochastic Learning on the Line' Strategies
2018
In this paper, we consider the problem of Distance Estimation (DE) when the inputs are the $x$ and $y$ coordinates (or equivalently, the latitudinal and longitudinal positions) of the points under consideration. The aim of the problem is to yield an accurate value for the real (road) distance between the points specified by the latter coordinates. 1 This problem has, typically, been tackled by utilizing parametric functions called the “Distance Estimation Functions” (DEFs). The parameters are learned from the training data (i.e., the true road distances) between a subset of the points under consideration. We propose to use Learning Automata (LA)-based strategies to solve the problem. In par…
Measuring foreland container port connectivity disaggregated by destination markets: An index for Short Sea Shipping services in Spanish ports
2020
Abstract The present research aims to develop a Foreland Port Connectivity Index (FPCI) including both qualitative and quantitative variables related to the characteristics of the maritime services provided. To that end, the FPCI incorporates two discount factors—the number of shipping services and destination countries—as penalties to correct for the quality of a port connection. After defining the FPCI, the index is applied to Spanish ports to study their connectivity in terms of container Short Sea Shipping (SSS) services. Although the connectivity of SSS traffic has not been widely studied, it is an interesting case study as small ports play a more relevant role in facilitating access t…
A more efficient cutting planes approach for the green vehicle routing problem with capacitated alternative fuel stations
2021
AbstractThe Green Vehicle Routing Problem with Capacitated Alternative Fuel Stations assumes that, at each station, the number of vehicles simultaneously refueling cannot exceed the number of available pumps. The state-of-the-art solution method, based on the generation of all feasible non-dominated paths, performs well only with up to 2 pumps. In fact, it needs cloning the paths between every pair of pumps. To overcome this issue, in this paper, we propose new path-based MILP models without cloning paths, for both the scenario with private stations (i.e., owned by the fleet manager) and that with public stations. Then, a more efficient cutting plane approach is designed for addressing both…
Branch-price-and-cut algorithms for the pickup and delivery problem with time windows and multiple stacks
2016
Abstract This paper proposes models and algorithms for the pickup and delivery vehicle routing problem with time windows and multiple stacks. Each stack is rear-loaded and is operated in a last-in-first-out (LIFO) fashion, meaning that when an item is picked up, it is positioned at the rear of a stack. An item can only be delivered if it is in that position. This problem arises in the transportation of heavy or dangerous material where unnecessary handling should be avoided, such as in the transportation of cars between car dealers and the transportation of livestock from farms to slaughterhouses. To solve this problem, we propose two different branch-price-and-cut algorithms. The first sol…
New exact methods for the time-invariant berth allocation and quay crane assignment problem
2019
Abstract Efficient management of operations in seaport container terminals has become a critical issue, due to the increase in maritime traffic and the strong competition between ports. In this paper we focus on two seaside operational problems: the Berth Allocation Problem and the Quay Crane Assignment Problem, which are considered in an integrated way. For the continuous BACAP problem with time-invariant crane assignment we propose a new mixed integer linear model in which the vessels can be moored at any position on the quay, not requiring any quay discretization. The model is enhanced by adding several families of valid inequalities. The resulting model is able to solve instances with u…
Irregular packing problems: a review of mathematical models
2020
Abstract Irregular packing problems (also known as nesting problems) belong to the more general class of cutting and packing problems and consist of allocating a set of irregular and regular pieces to larger rectangular or irregular containers, while minimizing the waste of material or space. These problems combine the combinatorial hardness of cutting and packing problems with the computational difficulty of enforcing the geometric non-overlap and containment constraints. Unsurprisingly, nesting problems have been addressed, both in the scientific literature and in real-world applications, by means of heuristic and metaheuristic techniques. However, more recently a variety of mathematical …
System Dynamics in the Predictive Analytics of Container Freight Rates
2021
This study proposes a two-tier cross-validation and backtesting procedure, including expanding and rolling-window test metrics in predictive analytics of container freight rates by utilizing the system dynamics approach. The study utilized system dynamics to represent the nonlinear complex structure of container freight rates for predictive analytics and performed univariate and multivariate time-series analysis as benchmarks of the conventional approach. In particular, the China containerized freight index (CCFI) has been investigated through various parametric methodologies (both conventional time-series and system dynamics approaches). This study follows a strict validation process cons…
Application of queuing methodology to analyze congestion: A case study of the Manila International Container Terminal, Philippines
2016
The objective of this paper is to apply queuing methodology in order to analyze congestion at the Manila International Container Terminal (MICT) in the Port of Manila, the Philippines. The vessels calling at the MICT have to wait in a queue before receiving services at berths because of congestion. For vessel operators and cargo owners this situation creates waiting time costs and delays in delivery of goods to final customers. One option to decrease waiting time is to expand capacity by increasing the number of berths. Construction of a new berth is a time consuming and costly procedure, which needs to be considered carefully before being implemented. To determine whether the data collecte…
The periodic rural postman problem with irregular services on mixed graphs
2019
Abstract In this paper, we deal with an extension of the rural postman problem in which some links of a mixed graph must be traversed a given number of times over a time horizon. These links represent entities that must be serviced a specified number of times in some subsets of days (or periods) of the time horizon. The aim is to design a set of minimum-cost tours, one for each day/period of the time horizon, that satisfy the service requirements. We refer to this problem as the periodic rural postman problem with irregular services (PRPP–IS). Some practical applications of the problem can be found in road maintenance operations and road network surveillance, for example. In order to solve …
Competition and cooperation for intermodal container transhipment: A network optimization approach
2018
Abstract This study presents an analysis of cross-border competition and cooperation between ports in Bangladesh and India. Nepal and Bhutan are countries without access to seaports — two landlocked countries in South Asia, depending solely on the Indian port of Kolkata for their international seaborne trade. Alternatives do exist in the Bangladeshi ports of Chittagong and Mongla but these are not exploited, in spite of trade agreements that allow access to a third country's port, and/or crossing the land of a third, intermediate, country. We formulate a mixed integer linear programming optimization model to find the optimum economic benefit of port users (serving Bhutan, Nepal and Northeas…