Abstract

A set of parameters to analyze business models of scientific publishers, especially those that offer open access to their content for all or some of their journals, is presented and defined. A definition of the term “business model” that exceeds the old conceptual restriction tied to funding sources is given. This more complete view of the business model requires extending the analysis of funding sources to other economic and financial components as well as operational and strategic dimensions of the publisher. This allows a better and more authoritative interpretation and analysis of the various business models of scientific publishers.

Abstract

The reliability of transit modes is a crucial issue to guarantee their competitiveness and attractiveness. Experience shows that buses covering busy lines with short headways tend to arrive irregularly at their stops, often in bunches and therefore remarkably affecting the service. Hence, this work presents a stochastic model capable of representing the operational activity of a bus transit network and the service disruptions which eventually end up causing deviations from desired schedule. At the same time, the model is tested on an ideal route as a decision making tool.

Abstract

International audience; High demand of flights on elementary air traffic control sectors results in high delays, extra-fuel burn and CO2 emissions, and may also lead to safety issues due to the destabilization of the aviation network. This paper presents a new control strategy approach to keep control of the current flight demand in European busiest sectors (Reims, Paris and Marseille sectors). Flow management positions in Area Control Centers suggest to airline operations centers delay-free routes for the most capacity impeding flights within the French airspace. Instead of spreading flight demand over time, this innovative approach aims at spreading the demand in space, relying on local expertise and enhanced collaboration. The trials conducted from July to September 2015 proved to be beneficial for airlines operations with more than 12,000 minutes of delay saved compared to summer 2014 while traffic increased by more than 6% from 9h to 13h UTC. Following Airport-Collaborative Decision Making, the Collaborative Advanced Planning process paves the way for the En-Route Collaborative Decision Making concept.

Abstract

Collisions between birds and aircraft pose a severe threat to aviation and avian safety. To understand and prevent these bird strikes, knowledge about the factors leading to these bird strikes is vital. However, even though it is a global issue, data availability strongly varies and is difficult to put into a global picture. This paper aims to close this gap by providing an in-depth review of studies and statistics to obtain a concise overview of the bird strike problem in commercial aviation on an international level. The paper illustrates the factors contributing to the occurrence and the potential consequences in terms of effect on flight and damage. This is followed by a presentation of the risk-reducing measures currently in place as well as their limitations. The paper closes with an insight into current research investigating novel methods to prevent bird strikes. Document type: Article

Abstract

Inefficient transport systems impose extra travel time for travelers, cause dissatisfaction and reduce service levels. In this study, the demand-oriented train scheduling problem is addressed using a robust skip-stop method under uncertain arrival rates during peak hours. This paper presents alternative mathematical models, including a two-stage scenario-based stochastic programming model and two robust optimization models, to minimize the total travel time of passengers and their waiting time at stations. The modeling framework accounts for the design and implementation of robust skip-stop schedules with earliness and tardiness penalties. As a case study, each of the developed models is implemented on line No. 5 of the Tehran metro, and the results are compared. To validate the skip-stop schedules, the values of the stochastic solution and the expected value of perfect information are calculated. In addition, a sensitivity analysis is conducted to test the performance of the model under different scenarios. According to the obtained results, having perfect information can reduce up to 16% of the value of the weighted objective function. The proposed skip-stop method has been shown to save about 5% in total travel time and 49% in weighted objective function, which is a summation of travel times and waiting times as against regular all-stop service. The value of stochastic solutions is about 21% of the value of the weighted objective function, which shows that the stochastic model demonstrates better performance than the deterministic model. Document type: Article