Study of predictors of taxi times at BCN Barcelona-El Prat Airport

Citation

Valenzuela-Arroyo, M., Lordan, O., Sallan, J. M. (2014). Study of predictors of taxi times at BCN Barcelona-El Prat Airport. 2014 ATRS World Conference. KEDGE Business School, Bordeaux, France.

Abstract

PURPOSE
This study develops a model to predict taxi in and out times at Barcelona-El Prat Airport. The model includes a set of variables that take into account the aspects that can affect taxi times, such as control areas, operation hours, type of aircraft, and others.

METHODOLOGY
The study has been carried out using airport’s daily operational data for the months of June, July and August 2013. After filtering the information, several linear regression models have been built which provide a predicted value of taxi times as a function of the predictors taken into account.

ANTICIPATED RESULTS
The area predictors combined with the hour of operation explain more than the 75% of variance of taxi times. Also, predictor models show that taxi times are greatly dependent on the type of operation.
The taxi in model has a stronger predictive power than the taxi-out model. Taxi-in accounts for 76% of variance and the mean error of residuals is 0.48 min, while the same values for taxi-out model are 45% and 2.16 min, respectively. The reason to be of these differences is the uncertainty produced by waiting times at runway headers in taxi out models, a variable that cannot be controlled.

KEYWORDS
Taxi Times, Linear Regression Model, Predictor, Barcelona-El Prat Airport

A study of pooling of repairable parts inventory between operators

Citation

Lopez-Gracia, N., Lordan, O., Sallan, J. M. (2014). A study of pooling of repairable parts inventory between operators. 2014 ATRS World Conference. KEDGE Business School. Bordeaux, France.

Abstract

PURPOSE
The purpose of providing availability inventory service is to maximize aircraft utilization by keeping spare units ready to be installed whenever and wherever needed. Since the size of the fleet supported by the spare repairable components inventory is the most important driver, we model the closed-loop inventory system in which component failures are Poisson distributed and the repair times at the service facility are exponential.

METHODOLOGY
 The method is based on Palm’s theorem for recommending a repairable operative inventory for a fleet and the model estimates parts demand during a certain period. In this research, we develop an inventory model for a repairable parts system which is shared by different operators in order to quantify the advantages of managing a “pool” inventory instead of private inventories for each customer.

ANTICIPATED RESULTS
Analysis of key parameters suggests that to improve the availability of the system with repairable spare parts, the supplier should improve the components repair facility, rather than the base stock level.

KEYWORDS
Inventory pooling, Component reliability, Repair facility, Poisson distribution

Analysis of robustness of alliance route networks

Citation

Lordan, O., Sallan, J. M.; Simo, P., Gonzalez-Prieto, D. (2014). Analysis of robustness of alliance route networks. 2014 ATRS World Conference. KEDGE Business School. Bordeaux, France

Abstract

PURPOSE
This study analyzes the robustness of the three major airline alliances (Star Alliance, oneworld and SkyTeam) route network to unintended errors and intentional attacks. Robustness is assessed in two ways: with an edge-betweenness based vulnerability scale, and with the evolution of the size of the giant component as a function of number of disconnected nodes.

METHODOLOGY
Network robustness is assessed in several ways. First, it is proposed a normalization of a multi-scale measure of the vulnerability in order to compare the performance of networks with different sizes. Second, several adaptive strategies are proposed to minimize the size of giant component with a given fraction of disconnected nodes. Together with other approaches found in the literature, a node selection criterion based on network efficiency is introduced. Finally, it is described a new procedure -the inverted adaptive strategy- for sorting the nodes in order to anticipate the breakdown of a network.

ANTICIPATED RESULTS
Results show that Star Alliance has the most resilient route network, followed by SkyTeam and oneworld. Besides, the inverted adaptive strategy based on the efficiency criterion -inverted efficiency- shows a good performance to break networks, similar or even better than the adaptive strategy based on node betweenness.

KEYWORDS
Airline alliances, route networks, robustness, airport closure.

Transformational leadership and organizational commitment: mediating role of leader-member exchange

Author

Imen Keskes

Supervisors

Jose M Sallan, Pep Simo

Defense date

1st October, 2014

Abstract

The thesis of Imen Keskes is a theoretical and empirical study of the relationship between transformational leadership (TL) and organizational commitment (OC). These two concepts are examined as multidimensional constructs and are empirically tested within a French speaking population. The main objective of this study is to examine the mechanisms through which dimensions of TL influence different forms of OC by testing the possible mediating role of leader member exchange (LMX). The present thesis consists of six chapters:

The first chapter introduces the concepts of TL, OC and LMX and the motivation for the research. It provides a brief summary of previous scientific work on the topic and it outlines the purpose and specific objectives of each chapter.

In the second chapter, a study and discussion of the relationship between leadership styles and OC  dimensions is carried out. An extensive literature research is performed in order to understand leadership and OC as well as the relationship between these two concepts. Although there is considerable research which suggest that TL is positively associated with OC in a variety of organizational settings and cultures, there is little empirical research focusing on the precise ways in which style of leadership impacts employee OC. Some critics about previous empirical and theoretical studies are presented and a number of areas for future research are developed.

In the third chapter, the English TL Questionnaire (TLQ) is translated into French using a back-translation technique. The validity and reliability of this instrument within two samples of French speaking populations (Tunisia and France) is tested. Internal consistency is assessed using Cronbach alpha coefficient. The construct validity is verified using the exploratory and confirmatory factor analysis. The results support a four-factor model of TLQ which consists of vision, supportive leadership, intellectual stimulation and personal recognition. These findings have shown adequate psychometric properties and have provided preliminary support for the construct validity of the proposed French version of the TLQ.

In the fourth chapter, the English OC Questionnaire (OCQ) is translated into French and the validity and reliability of this instrument within the two samples of  French speaking population is tested. The results have supported a 4-factor model of OCQ of the original questionnaire. These findings have shown adequate psychometric properties and have provided preliminary support for the construct validity of the proposed French version of the OCQ.

In the fifth chapter, some models that take into account the diverse dimensions of TL and the different forms of OC are proposed and tested by examining the role of LMX as a mediator between them. To verify the models, two types of validity tests are considered: the convergent validity and the discriminant validity. To test the direct hypothesis, the significance of the beta parameters in the structural models is assessed. To test the mediation hypothesis, two methods are used: Baron and Kenny method and a the comparison of nested structural models. The results confirm the significance of the proposed models. These findings are important since previous research did not test these variables together.

Finally, the last chapter summarizes the contribution of the thesis. The possible directions of further research work are also discussed in brief.

Thesis contents