Minh Hoang Ha

An exact algorithm and a metaheuristic for the multi-vehicle covering tour problem with a constraint on the number of vertices

The multi-vehicle covering tour problem (m-CTP) involves finding a minimum-length set of vehicle routes passing through a subset of vertices, subject to constraints on the length of each route and the number of vertices that it contains, such that each vertex not included in any route lies within a given distance of a route. This paper tackles a particular case of m-CTP where only the restriction on the number of vertices is considered, i.e., the constraint on the length is relaxed. The problem is solved by a branch-and-cut algorithm and a metaheuristic. To develop the branch-and-cut algorithm, we use a new integer programming formulation based on a two-commodity flow model. The metaheuristic is based on the evolutionary local search (ELS) method proposed in [23]. Computational results are reported for a set of test problems derived from the TSPLIB.

Designing service sectors for daily maintenance operations in a road network

The problem of designing service sectors in a road network for the organisation of route maintenance activities is addressed in this paper. The decisions involve determining the locations of a set of depots and assigning road segments to the selected depots to form service sectors. Routing operations must be taken into consideration while partitioning service sectors in order to precisely evaluate deadhead and required number of vehicles. The problem is thus formulated as a location-arc routing problem and solved by a branch-and-cut algorithm. A three-stage heuristic algorithm with sector design component is developed to solve the medium- and large-sized problems. The computational experiments demonstrate the effectiveness of the heuristic algorithm, and the superiority of the heuristic algorithm to the exact method in terms of some specific partition evaluation criteria.

Improving the connectivity of a bus system: a case study of Ho Chi Minh city

Public transportation modes like buses plays an important role in our real life. Designing a good bus system can bring advantages to both passengers and the society. One of key design criteria is the connectivity which can be measured by the minimum number of bus lines a passenger must take to travel from one station to another. This paper considers the bus system design problem with the objective of improving the connectivity of the system from the existing infrastructure. We defined the problem in the form of an optimization problem and propose an algorithm for the solution. Results obtained from the real instances derived from the bus system of Ho Chi Minh city are analysed and reported.

New fast heuristics for the 2d strip packing problem with guillotine constraint

In this paper, we propose new and fast level-packing algorithms to solve the two-dimensional strip rectangular packing problem with guillotine constraints. Our methods are based on constructive and destructive strategies. The computational results on many different instances show that our method leads to the best results in many cases among fast heuristics.