Scheduling Jobs with Variable Job Processing Times on Unrelated Parallel Machines

m unrelated parallel machines scheduling problems with variable job processing times are considered, where the processing time of a job is a function of its position in a sequence, its starting time, and its resource allocation. The objective is to determine the optimal resource allocation and the optimal schedule to minimize a total cost function that dependents on the total completion (waiting) time, the total machine load, the total absolute differences in completion (waiting) times on all machines, and total resource cost. If the number of machines is a given constant number, we propose a polynomial time algorithm to solve the problem

Controllable Processing Times in Project and Production Management: Analysing the Trade-Off between Processing Times and the Amount of Resources

The amount of resources assigned to a task highly influences its processing time. Traditionally, different functions have been used in the literature in order to map the processing time of the task with the amount of resources assigned to the task. Obviously, this relation depends on several factors such as the type of resource and/or decision problem under study. Although in the literature there are hundreds of papers using these relations in their models or methods, most of them do not justify the motivation for choosing a specific relation over another one. In some cases, even wrong justifications are given and, hence, infeasible or nonappropriated relations have been applied for the different problems, as we will show in this paper. Thus, our paper intends to fill this gap establishing the conditions where each relation can be applied by analysing the relations between the processing time of a task and the amount of resources assigned to that task commonly employed in the production and project management literature

Post-seismic response and repair of earthquake-damaged reinforced concrete bridges

“In bridge structures, column members are typically designed to be the primary source of energy dissipation during an earthquake. Therefore, reinforced concrete (RC) bridges that are damaged in an earthquake tend to have damage to the column members. While many studies have been conducted on seismic strengthening of RC bridge columns, most are focused on retrofit instead of repair. In addition, the limited research on seismic repair of RC bridges has focused on evaluating the response of individual columns (member level), not the bridge structure (system level), due to limitations in modeling and especially testing of full bridge structures. Local modifications (interventions) from the repair of a member can change its performance, and changes in column member performance can influence the bridge structure performance, especially under seismic loading. This study evaluated the impact of RC bridge column seismic repair on the member level, system level, and community level responses. Numerical simulation was used to model the response of repaired RC bridge columns (member level) and study the post-repair response of a prototype bridge with repaired columns (system level). The model was also extended to develop a methodology to minimize the level of pre-earthquake retrofit such that the RC bridge can withstand an earthquake without collapse, suffering minor or moderate damage that can be rapidly repaired later. Finally, a discrete-event-based simulation model was developed to estimate the time needed to bring the situation under control for a given volume of resources under a variety of scenarios after an earthquake occurs in a case-study community (community response), and to study the sensitivity of the restoration times to different variables”--Abstract, page iii