Equacions estructurals amb lavaan

Resum

L'anàlisi d'equacions estructurals és una tècnica per avaluar models amb relacions complexes entre variables (path analysis), amb variables observables i variables latents. Un cas especialment interessant d'aplicació és l'anàlisi factorial confirmatòria, que permet avaluar la validesa de constructe d'escales de mesura. En aquest article es presenta el paquet de R lavaan, que permet avaluar amb facilitat models d'equacions estructurals. Es reporta informació sobre la sintaxi del model, així com de les possibilitats del paquet.

Enllaç a UPCommons

http://hdl.handle.net/2117/22726

Airline route networks: A complex network approach

Author

Oriol Lordan

Supervisors

Jose M Sallan, Pep Simo

Defense date

14th April, 2014

Abstract

Communication via air routes is an important issue in a world organized around a web-like city network. In this context, the robustness of network infrastructures, e.g. air transport networks, is a central issue in transport geography. Disruption of communication links by intentional causes (e.g., terrorist attack on an airport) or unintentional (e.g., weather inclemency) could be a serious drawback for countries, regions or airlines. Policymakers and the management of airlines and alliances should be able to reduce the effects of such interruptions in order to ensure good communication through air transport, that is, to maximize the robustness of their network at a reasonable cost. The literature review of the study of air transport route networks through complex networks has highlighted a lack of contributions to the study of the topology and the robustness of such networks, which contrasts with advances undertaken for other transport networks or communication systems. The literature survey suggests areas in which research should be undertaken, based on the existing literature in other areas and from three different perspectives: global route networks, airline alliances and airlines. The aim of this research is to develop a better understanding of air traffic and, in particular, to be able to assess the potential damage of any airport being inoperative for a continent, country or airline. This thesis analyzes the topology and robustness of three proposed levels of study characterized by different units of analysis: global route network, airline alliances route network and airlines route network. The different levels do not only represent networks of different magnitudes in number of nodes (airports) and links (routes), but also represent different approaches. In Chapter 2 robustness of the global air transport network (L1) has been analyzed and criteria based on Bonacich power centrality has been presented in order to assess attack vulnerability of complex networks. One of the outcomes of this study will be a list of the most critical airports for the vulnerability of the entire air transport network. In Chapter 3 robustness of alliances route network (L2) will be assessed comparing the robustness of the three major airline alliances (Star Alliance, oneworld and SkyTeam). To perform this analysis, one new node selection criterion based on the efficiency of networks and one new method of assessing vulnerability will be presented. This analysis will lead also to a comparison of the robustness of the three alliances. Finally, in Chapter 4 robustness of 10 FSCs and 3 LCCs route network (L2) will be analyzed. The studied FSCs belong to the different airline alliances showed in Chapter 3 thus allowing the comparison among levels. This chapter outlines a comparison of the differences in robustness between FSCs and LCCs. In Chapter 5 a summary and discussion of conclusions obtained for each level will be carried out.

Thesis contents

The complete text of this thesis can be dowloaded at the TDR repository in the following link: http://www.tdx.cat/handle/10803/144526

Study of the evolution of routes operated by an airline going into bankruptcy: the case of Spanair

Student

Cristina Alemany

Supervisors

Oriol Lordan / Jose M Sallan

Defense date 

11th Abril, 2014

Abstract

The aim of this project is to analyze the competitive dyamics that evolve when an airline goes bankrupt. The cease of operations of the bankrupt airline gives an opportunity to the rest of airlines to increase the market share of the routes covered by the airline. If the bankrupt airline belongs to an alliance, these routes may be covered by other members of the aliance, competitors or airlines operating on a point-to-point basis.

This project analyzes in depth the case of Spanair, an Spanish airline went bankrupt on January 2012. The route portfolio of the company of the period January 2010 - January 2012 is considered for analysis. Results shows that LCCs (Vueling and Ryanair) and FSC from onewold (Iberia) and SkyTeam (Air Europa) absorbed the market share left by Spanair. Other companies from Star Alliance absorbed a fraction of the international routes of Spanair, but none of the domestic routes. Currently Star Alliance has a weak position in Spain, since there is no local airline in this alliance.