Forecasting of taxi times: The case of Barcelona-El Prat airport

Citation

Lordan, Oriol; Sallan, Jose M; Valenzuela-Arroyo, Marta (2016). Forecasting of taxi times: The case of Barcelona-El Prat airport. Journal of Air Transport Management. 56(B), 118-122.

doi: http://dx.doi.org/10.1016/j.jairtraman.2016.04.015

Abstract

One of the challenges that air transport management is facing is to develop predictive tools for ground operations of aircraft, in particular of estimation of taxi times. The aim of this paper is to define a forecasting model for taxi times for a specific airport: Barcelona-El Prat. This model uses log-linear regression analysis to estimate taxi times with variables that can be computed before operation to account for route- and interaction-specific factors influencing taxi time. The resulting model has a strong predictive validity, but requires a sample size covering an extensive time of airport operations. The model results show that route-specific factors are useful to estimate taxi times, and the combination of stand and rapid exit variables (for landings) and runway (for take offs) accounts for a great part of the variability of taxi times.

Change-oriented organizational citizenship behavior: Analysis of antecedents centered on regulatory theory focus at the workplace

Citation

Simo, Pep; Sallan, Jose M; Fernandez, Vicenc; Enache, Mihaela (2016). Change-oriented organizational citizenship behavior: Analysis of antecedents centered on regulatory theory focus at the workplace. International Journal of Organizational Analysis, 24(2), 261-273.
doi: http://dx.doi.org/10.1108/IJOA-10-2014-0805

Abstract

Purpose – The aim of this research is to empirically examine the relationships between the regulatory focus in the workplace and discretionary (change-oriented OCB) and non-discretionary (intentions related to performance at work) work outcomes, in an academic work setting.

Design/methodology/approach – Data were collected using a questionnaire conducted with 251 Spanish academic workers. The data were analyzed using structural equation modeling.

Findings – Results reveal the existence of positive relationships between promotion focus and two of the outcomes: change-oriented OCB and research-oriented performance-enhancement intention. On the other hand, prevention focus had only a significant relationship with teacher-oriented performance-enhancement intention.

Research limitations/implications – The limitations of this research are twofold: on the one hand, further research should overcome the methodological limitations related with data gathering, looking for third-party measures of performance and favoring longitudinal data collection designs. On the other hand, more research is needed on the malleability of regulatory focus, defining models in which prevention and promotion focus act as mediating variables.

Practical implications – Individuals with high levels of promotion focus will put their efforts on the tasks which are more valued in the processes of tenure, promotion and compensation. On the other hand, individuals with high levels of prevention focus will tend to meet the minimum of requirements and accomplish salient job duties. These implications can be taken into account when defining human resource policies, giving a high weight in the assessment of tenure and promotion programs to those tasks on which the organization wants their promotion focus individuals to center their attention.

Originality/value – This paper is one of the first efforts of validating the regulatory focus of work scale in organizational and academic contexts different from the initial validation study. The study also contributes to research on the antecedents of change-oriented organizational citizenship behaviors, and defines new measures of intentions to perform in specific working activities.

Algoritmos genéticos

Esta cita de Darwin resume en una frase el funcionamiento de los algoritmos genéticos.

Probabilidad de empate

En relación al empate que hoy se ha producido en la asamblea de la CUP, lamentamos tener que desmentir afirmaciones como esta:



La probabilidad de que se haya producido este empate no es tan baja como indica Mario Bilbao. La probabilidad de que determinado número de asistentes a la asamblea vote por la investidura de Mas es función de la probabilidad p de que cada uno de los miembros de la asamblea desee investir presidente a Mas: los resultados habrían sido muy distintos si todos los asistentes estuvieran convencidos de investir a Mas (p próxima a 1) o de no investirlo (p próxima a 0). Para determinar la probabilidad de que exactamente 1515 de los 3030 asistentes hayan votado por la investidura de Mas, hemos de utilizar la distribución de probabilidad binomial.

El siguiente gráfico muestra la probabilidad de que se produzca empate (prob) en función de la probabilidad de que un miembro de la asamblea desee que Mas sea investido (p):



Como Antoni Ítalo (entre otros) ha indicado, la probabilidad de empate es como máximo del 1,45%, y es (ahora sí) prácticamente despreciable si p no está entre 0,47 y 0,52 aproximadamente.

The Spanish corporate structure through interlocking directorates

Citation

Sicilia, Carlos; Sallan, Jose M.; Simo, Pep (2016). The Spanish corporate structure through interlocking directorates. Cuadernos de Gestión, 63(1):63-84.
DOI: http://dx.doi.org/10.5295/cdg.120336ps

Abstract

The objective of this paper is to determine to what extent globalisation pressures are changing networks modelled on continental capitalism into Anglo-Saxon models. For this purpose we analyse the Spanish network of interlocks, comparing the present structure with that of 1993. We show how, although Spanish corporative structure continues to display characteristics of the continental economies, some major banks are significantly reducing industrial activity. Nevertheless, the financial organisations continue to maintain a close relationship with sectors such as construction and services. According to the theories on the role of the interlocking directorates, the companies in these sectors assure their access to banking credit by incorporating advisors from financial organisations to their board of directors.

El objetivo de este trabajo es determinar en qué medida las presiones de la globalización han cambiado los modelos que siguen las redes corporativas españolas desde los propios del capitalismo continental hacia los modelos anglosajones. Para ello se analiza la red española de consejerías cruzadas, comparando la estructura actual con la de 1993. Se muestra cómo, a pesar de la estructura corporativa española continúa mostrando características de las economías continentales, algunos de los principales bancos están reduciendo significativamente la actividad industrial. No obstante, las entidades financieras siguen manteniendo una estrecha relación con sectores como la construcción y los servicios. De acuerdo con las teorías sobre el papel de las consejerías cruzadas, las empresas de estos sectores tratan de asegurar su acceso al crédito bancario mediante la incorporación de asesores de las entidades financieras a su consejo de administración.

Combinatorial explosion

Combinatorial optimization is about picking one element of a set of finite objects that optimizes an objective function. Put in this way, the solution may seem straightforward: just enumerate all elements of the set and assess the objective function for each object.

The problem with this naïve approach is that the number of elements of the set can be very large. Let's consider, for instance, the symmetric travelling salesperson problem. For an instance of n nodes, the number of possible solutions is the factorial of (n-1) divided by two. This means that, for a problem of size n=20, and taking one millisecond to assess each solution, it takes around 1,108,606 years to assess all solutions. This effect is called combinatorial explosion.

This video shows an example of an even faster combinatorial explosion. Additionally, helps in learning how to count large numbers in Japanese...

Modeling and Solving Linear Programming with R

Citation

Sallan, Jose M.; Lordan, Oriol; Fernandez, Vicenc (2015). Modeling and Solving Linear Programming with R. Omniascience.

Abstract

Linear programming is one of the most extensively used techniques in the toolbox of quantitative methods of optimization. One of the reasons of the popularity of linear programming is that it allows to model a large variety of situations with a simple framework. Furthermore, a linear program is relatively easy to solve. The simplex method allows to solve most linear programs efficiently, and the Karmarkar interior-point method allows a more efficient solving of some kinds of linear programming. The power of linear programming is greatly enhanced when came the opportunity of solving integer and mixed integer linear programming. In these models all or some of the decision variables are integers, respectively.

In this book we provide a brief introduction to linear programming, together with a set of exercises that introduce some applications of linear programming. We will also provide an introduction to solve linear programming in R. For each problem a possible solution through linear programming is introduced, together with the code to solve it in R and its numerical solution.

Availability

Please see Omniascience website for details, and the repository containing the code used in the book.

Also available through UPCommons in this direction.