Car Sequencing Problem con flotas de vehículos especiales. Presentación

Car Sequencing Problem con demanda parcial incierta. Robustez en una multi-secuencia de vehículos mixtos.Partiendo del Car Sequencing Problem (CSP), introducimos el concepto demanda parcial incierta a través de la incorporación de Flotas de vehículos especiales en un plan de demanda. Tras resaltar las peculiaridades de una Flota y establecer las hipótesis de trabajo, proponemos un modelo de programación lineal entera mixta orientado a satisfacer el máximo número de restricciones CSP. Posteriormente, introducimos el concepto multi-secuencia de producción y proponemos funciones para medir su robustez. La versión robusta del CSP considera un conjunto de escenarios de la demanda para las Flotas y presenta funciones que miden el exceso sobre el requerimiento estándar de las opciones del CSP en planes de demanda, opciones concretas y ciclos de fabricación. Dichas funciones pueden emplearse como función objetivo en problemas de optimización y como métricas ante una muli-secuencia de producción concreta.Preprin

- CONVERGENCE IN OECD COUNTRIES: TECHNICAL CHANGE, EFFICIENCY AND PRODUCTIVITY

The aim of this study is to analyze labor productivity convergence in the countries of the OECD over the period 1965-90. A non-parametric frontier approach is used to calculate the Malmquist productivity index. By breaking it down, the contribution to the growth of labor productivity of technical progress, of changes in efficiency, and of the accumulation of inputs per worker are quantified. Unlike other studies, the results obtained show that technical change has worked against labor productivity convergence, since it has always been greater in the countries with higher labor productivity. El trabajo tiene como objetivo básico analizar la contribución de las distintas fuentes del crecimiento a la convergencia en productividad del trabajo en los países de la OCDE en el periodo 1965-90. Más concretamente, y utilizando dos aproximaciones frontera distintas (índices de productividad de Malmquist y un enfoque de frontera estocástica), se distingue la contribución del cambio técnico y de los cambios de eficiencia a la convergencia en productividad del trabajo. Los resultados obtenidos contradicen los obtenidos en otros trabajos que utilizan aproximaciones no frontera a la medición de la productividad, rechazándose la existencia de convergencia tecnológica, dado que el progreso técnico ha sido mayor en los países con mayor productividad del trabajo.Convergencia, cambio técnico, eficiencia, índice Malmquist de productividad Convergence, technical change, efficiency, Malmquist productivity index

- EFICIENCY AND PRODUCTIVITY SPECIALIZATION: THE SPANISH REGIONS

This paper shows the importance of the composition of production -productive specialization- and sector inefficiencies when evaluating efficiency in aggregate production. For this purpose, a new approach is proposed for obtaining efficiency scores which enables two components to be differentiated: one associated with the degree of efficiency within each sector -intra-sector efficiency- and another associated with the composition of production - composition efficiency. The application of this approach and its break-down for the Spanish regions in the period 1964-1993, using a non-parametric approach -DEA- shows greater gainsin composition efficiency as a consequence of the structural changes in productive specialization. Also, the break-down of labor productivity convergence shows the increasing importance over time of composition efficiency as a source of convergence, being even more important than capital accumulation and technical progress from the mid-1970s. Nevertheless, intra-sector efficiency gains was a significant source of convergence for the whole period analysed. Este trabajo muestra la importancia que la composición de la producción -especialización productiva- y las ineficiencias sectoriales tienen a la hora de valorar la eficiencia en la producción agregada. Para ello, se propone una nueva forma de medir la eficiencia que permite diferenciar dos componentes: uno asociado al grado de eficiencia dentro de cada sector -eficiencia intrasectorial- y otro asociado a la composición de la producción - eficiencia de composición-. La aplicación de este indicador y su decomposición para las regiones españolas en el periodo 1964-93 utilizando un enfoque no paramétrico -DEA-muestra las mayores ganancias de eficiencia de composición como consecuencia de los cambios estructurales en la especialización productiva. Asimismo, la descomposición de la convergencia en productividad del trabajo muestra una importancia creciente a lo largo del tiempo de la eficiencia de composición como fuente de convergencia siendo incluso más importante que la acumulación de capital y el progreso técnico desde mediados de la década de los setenta. No obstante, para la totalidad del periodo analizado la eficiencia intrasectorial ha sido una fuente significativa de convergencia.Eficiencia, especialización productiva, convergencia Efficiency, productive specialisation, convergence

- HUMAN CAPITAL IN OECD COUNTRIES: TECHNICAL CHANGE, EFFICENCY AND PRODUCTIVITY

The aim of this paper is to analyse the role of human capital in the productivity gains of the countries of the OECD in the period 1965-90, breaking down the productivity gains into technicalchange and gains in efficiency. For this purpose we use both a stochastic frontier production function and a non-parametric approach and calculate Malmquist indices of productivity. Theresults obtained indicate the existence of both a level effect and a rate effect (a higher level of human capital affects positively the rate of technical progress) associated with human capital. Thedifferences among countries in endowments of human capital have worked against labour productivity convergence, since the richer countries, thanks to their greater endowment of human capital, have experienced higher rates of technical progress. El objetivo de este trabajo es analizar el papel del capital humano en las ganancias de productividad de los países de la OCDE en el periodo 1965-90, descomponiendo las ganancias de productividad en cambio técnico y ganancias de eficiencia. Para ello se estima tanto una función de producción frontera de carácter estocástica como una aproximación no paramétrica y se calculan índices de Malmquist de productividad. Los resultados obtenidos indican la existencia tanto de un efecto nivel como de un efecto tasa (un mayor nivel de capital humano afecta positivamente a la tasa de progreso técnico) asociada al capital humano. Las diferencias de dotaciones de capital humano entre países han actuado en contra de la convergencia en productividad del trabajo ya que los países más ricos, gracias a su mayor dotaciones de capital humano, han experimentado tasas mayores de progreso técnico.Cambio técnico, eficiencia, productividad. Technical change, efficiency and productivity

Benefits of robust multiobjective optimization for flexible automotive assembly line balancing

“This is a pre-print of an article published inJ. Flex Serv Manuf. The final authenticated version is available online at: https://doi.org/10.1007/s10696-018-9309-y ” Chica, M., Bautista, J. & de Armas, J. Flex Serv Manuf J (2018). https://doi.org/10.1007/s10696-018-9309-yChanging conditions and variations in the demand are frequent in real industrial environments. Decision makers have to take into account this uncertainty and manage it properly. One clear example is the automotive industry where manufacturers have to assume an uncertain and heterogeneous demand. For instance, automotive manufacturers must adapt their decisions when balancing the assembly line by considering different flexible solutions. Our proposal is using robust multiobjective optimization and simulation techniques to provide managers with a set of robust and equally-preferred solutions for assembly line balancing. We study a Nissan case where the demand of each product family is uncertain. The problem is addressed by considering a robust multiobjective model for assembly line balancing based on a high number of production plans. After the selection of six different assembly line configurations, we study the implications of robustness metrics based on workstations’ overload. We show that the adverse managerial effects of not having flexible line configuration when demand changes are alleviated. For the real Nissan automotive case, our analysis and conclusions show the managerial and industrial benefits of using robust assembly lines. We also encourage decision makers to use robust multiobjective optimization methods for selecting the most flexible decisions.Peer ReviewedPostprint (author's final draft

Appendices for “Benefits of robust multiobjective optimization for flexible automotive assembly line balancing”

Postprint (published version

Métricas sobre la robustez de soluciones en el problema TSALB ante la variación del mix de producción

Aplicación de métricas de robustez a configuraciones de línea en TSALBP - Ejemplo prototipo.Partiendo de la familia de modelos TSALBP (Time and Space Assembly Line Balancing Problem), proponemos diversas funciones para medir la robustez de un equilibrado de línea atendiendo a sus atributos temporales y espaciales. La versión robusta de TSALBP considera un conjunto de escenarios de demanda y presenta funciones que miden el exceso de carga, tanto temporal como espacial, en las estaciones de trabajo de la línea. Dichas funciones pueden emplearse como funciones objetivo en el problema de optimización resultante y como métricas ante un equilibrado de línea concreto; en ambos casos, la nueva versión de TSALBP pone a disposición del decisor nuevas soluciones de equilibrado más eficientes y robustas ante una demanda incierta.Preprin

A systematic review on nomophobia prevalence: Surfacing results and standard guidelines for future research.

[EN]Mobile phones allow us to stay connected with others and provide us a sense of security. We can work, chat with family and friends, take pictures, buy clothes or books, and even control home appliances. They play such a significant role in our lives that we feel anxious without them. In some cases, the relationship between humans and these communication devices have become problematic. Nomophobia (NMP) is the fear of becoming incommunicable, separated from the mobile phone and losing connection to the Internet. Since this social phobia was coined in the first decade of the XXI century, a growing number of studies have studied it and reported the prevalence of this technology-related problem. However, this research activity has generated mixed results regarding how we assess and report nomophobia and who may be at a higher risk of suffering or developing it. We conducted a systematic review of 108 studies published in English and Spanish and collected them in Parsifal. We searched for assessment and prevalence data on nomophobia. Also, we looked at gender and age differences to identify risk factors and see if these differences exist and emerge worldwide. In this study, we find that women and younger individuals suffer more from nomophobia. The disparity in reporting the prevalence of nomophobia is enormous since the percentages of "at-risk" participants go from 13% to 79%, and participants suffering from it are between 6% and 73%, being the score in the range of 45.5 and 93.82. Within the group of nomophobic people, moderate cases vary between 25.7% and 73.3%, and severe cases, between 1% and 87%. Such disparity is due to differences in assessment criteria. Females and young people seem to be more vulnerable to nomophobia although methodological disparity makes it difficult to reach definitive conclusions. We conclude our review by recommending some common guidelines for guiding future research.This research was funded by the Spanish Ministry of Economy, Industry and Competitiveness, RTI2018-094212-B I00: (CIBER-AACC), and PID2019-107589GB-I00, and it was also supported by the International University of La Rioja, Project Cyberpsychology (Triennium 2017-2020)

Evaluation of physichochemical parameters influencing bulking episodes in a municipal wastewater treatment plant

A study of physicochemical parameters in a municipal wastewater treatment plant was undertaken to consider the presence of bulking phenomena by means of statistical and logistic regression analyses. There appears to be an important effect on activated sludge settleability that can be related to the temperature of wastewater. Besides, there were significant differences between the percentage of nitrogen removal from the secondary treatment with the season. The SVI increased with conductivity, meanwhile BOD5 removal decreased with this parameter. The development of logistic regression models identified two statistically significant variables that appeared to be important to the contribution of a higher SVI: season and pH

Design, implementation and evaluation of a web-based computer-tailored intervention to prevent binge drinking in adolescents: study protocol

Background: Binge-drinking in adolescents is a highly prevalent healthcare problem that associates physical and mental health complications with community implications. This paper describes the design, implementation and evaluation of the first web-based computer tailored intervention aimed at the prevention of binge drinking in Spanish adolescents. Methods: The Alerta Alcohol program is based on the I-Change Model. First, feedback from focus and Delphi groups are used for cultural adaptation and to obtain further information on the items to be included on the program. A pilot study is then conducted to assess feasibility and to identify strengths and weaknesses. Second, a Cluster Randomized Controlled Trial is conducted to test the effectiveness of Alerta Alcohol in students aged 16 to 18 years. The study is performed in 16 high schools from Andalusia (southern Spain), which are randomized either to the experimental or the control condition (EC and CC). The EC receives the Alerta Alcohol intervention, which consists of four sessions at school (baseline questionnaire, two sessions in three scenarios: at home, celebrations, and public places, and a final evaluation). The adolescents are provided with answers related to their views of each scenario; this information is used to provide highly specific feedback regarding their knowledge, risk perception, self-esteem, attitude, social influence, and self-efficacy. In addition, two booster sessions are given at home to reinforce the previous messages. The CC just completes the baseline and the final evaluation questionnaires and then they are allowed to receive the intervention as well (as a waiting list). Evaluation takes place after four months. The primary endpoint is binge drinking within 30 days prior to the evaluation and alcohol use in the previous week. It is expected that Alerta Alcohol reduce the prevalence of binge drinking by 10%. Follow up analyses are carried out to determine the differences in effectiveness according to the compliance of the program (quality of the implementation). Discussion: The results are expected to be applicable and may incorporate improvements in the practice of the Healthcare and Education Systems. If the program proves to be effective, regional and eventual national implementation should be considered.Junta de Andalucia PI-0031-201