Routing trains through a railway station based on a Node Packing model

In this paper we describe the problem of routing trains through a railway station. This routing problem is a subproblem of the automatic generation of timetables for the Dutch railway system. The problem of routing trains through a railway station is the problem of assigning each of the involved trains to a route through the railway station, given the detailed layout of the railway network within the station and given the arrival and departure times of the trains. When solving this routing problem, several aspects such as capacity, safety, and customer service have to be taken into account. In this paper we describe this routing problem in terms of a Weighted Node Packing Problem. Furthermore, we describe an algorithm for solving this routing problem to optimality. The algorithm is based on preprocessing, valid inequalities, and a branch-and-cut approach. The preprocessing techniques aim at identifying super uous nodes which can be removed from the problem instance. The characteristics of the preprocessing techniques with respect to propagation are investigated. We also present the results of a computational study in which the model, the preprocessing techniques and the algorithm are tested based on data related to the railway stations Arnhem, Hoorn and Utrecht in the Netherlands.mathematical economics and econometrics ;

Interview with Liberato "Libby" Viduya

Interview conducted in English.Interview conducted at Pearl City, Oʻahu.Liberato C. Viduya, Jr., second of four children, was born in 1937, in Lānaʻi City, Lānaʻi. His father, Liberato Viduya, Sr., who emigrated from the Philippines, was employed by Hawaiian Pineapple Company. Starting as a field laborer, he rose up the ranks to luna. His mother, Loreta Viduya, a Filipino immigrant raised and educated on Maui, held various jobs, including that of court interpreter. The Viduyas actively participated in community, school, and church-related activities. Liberato C. Viduya, Jr., grew up in the Stable Camp area of Lānaʻi City. He attended Lānaʻi High and Elementary School. As a high school senior in 1955, he was awarded first place in public speaking at the National Future Farmers of America Conference in Kansas City, Missouri. He earned BA and MEd degrees from the University of Hawaiʻi at Mānoa. During a forty-five-year career with the Hawaiʻi State Department of Education, he held various positions: teacher, counselor, and principal; assistant superintendent for the Office of Instructional Services; and superintendent for Central and Leeward Districts on Oʻahu. He and wife, Loretta, have one daughter and three grandchildren. The Viduyas reside in Pearl City, Oʻahu

Integrated Lot Sizing in Serial Supply Chains with Production Capacities

We consider a model for a serial supply chain in which production, inventory, and transportation decisions are integrated in the presence of production capacities and concave cost functions. The model we study generalizes the uncapacitated serial single-item multilevel economic lot-sizing model by adding stationary production capacities at the manufacturer level. We present algorithms with a running time that is polynomial in the planning horizon when all cost functions are concave. In addition, we consider different transportation and inventory holding cost structures that yield improved running times: inventory holding cost functions that are linear and transportation cost functions that are either linear, or are concave with a fixed-charge structure. In the latter case, we make the additional common and reasonable assumption that the variable transportation and inventory costs are such that holding inventories at higher levels in the supply chain is more attractive from a variable cost perspective. While the running times of the algorithms are exponential in the number of levels in the supply chain in the general concave cost case, the running times are remarkably insensitive to the number of levels for the other two cost structures.lot sizing, integration of production planning and transportation, dynamic programming, polynomial time algorithms

Models and solution techniques for frequency assignment problems

Wireless communication is used in many different situations such as mobile telephony, radio and TV broadcasting, satellite communication, wireless LANs, and military operations. In each of these situations a frequency assignment problem arises with application specific characteristics. Researchers have developed different modeling ideas for each of the features of the problem, such as the handling of interference among radio signals, the availability of frequencies, and the optimization criterion. This survey gives an overview of the models and methods that the literature provides on the topic. We present a broad description of the practical settings in which frequency assignment is applied. We also present a classification of the different models and formulations described in the literature, such that the common features of the models are emphasized. The solution methods are divided in two parts. Optimization and lower bounding techniques on the one hand, and heuristic search techniques on the other hand. The literature is classified according to the used methods. Again, we emphasize the common features, used in the different papers. The quality of the solution methods is compared, whenever possible, on publicly available benchmark instances

Models and Solution Techniques for Frequency Assignment Problems

Wireless communication is used in many different situations such as mobile telephony, radio and TV broadcasting, satellite communication, and military operations. In each of these situations a frequency assignment problem arises with application specific characteristics. Researchers have developed different modeling ideas for each of the features of the problem, such as the handling of interference among radio signals, the availability of frequencies, and the optimization criterion. This surve