Evaluating urban freight transport policies within complex urban environments

Urban Freight Transport (UFT) entails significant advantages for the economic growth of cities, but can also hamper population quality of life, obstructing vehicles and people movements while exacerbating environmental problems. Many initiatives have been engaged by many city administrators in order to efficiently manage UFT, evaluating different policies at a global scale. From the perspective of operators, most works analyze a limited set of policies or only focus on the benefits of companies. In this work, a decisionmaking process is used to evaluate a large set of UFT policies, through different attributes representing the advantages and limitations of each policy over promoter companies and the society. To do so, an ex-ante procedure in five steps is proposed to classify the policies: (1) attributes definition, (2) attributes weighting, (3) policy-attribute assessment, (4) policy ranking, and (5) feasibility threshold satisfaction. The whole process is supported on consultations to 26 experts regarding shop supply and restocking activities within complex urban environments. Results show a classification of the analyzed policies, according to their suitability for implementation ; which could be extended (directly or with small adjustments) to other contexts, given the flexibility of the decision-making procedure developed.Peer ReviewedPostprint (author's final draft

A MILP model for the teacher assignment problem considering teachers’ preferences

The Teacher Assignment Problem is part of the University Timetabling Problem and involves assigning teachers to courses, taking their preferences into consideration. This is a complex problem, usually solved by means of heuristic algorithms. In this paper a Mixed Integer Linear Programing model is developed to balance teachers’ teaching load (first optimization criterion), while maximizing teachers’ preferences for courses according to their category (second optimization criterion). The model is used to solve the teachers-courses assignment in the Department of Management at the School of Industrial Engineering of Barcelona, in the Universitat Politècnica de Catalunya. Results are discussed regarding the importance given to the optimization criteria. Moreover, to test the model's performance a computational experiment is carried out using randomly generated instances based on real patterns. Results show that the model is proven to be suitable for many situations (number of teachers-courses and weight of the criteria), being useful for departments with similar requests.Peer ReviewedPostprint (author's final draft

A community electrification project: combination of microgrids and household systems fed by wind, PV or micro-hydro energies according to micro-scale resource evaluation and social constraints

When electrifying isolated rural communities, usually standardized solutions have been implemented using the same technology at all the points. However these solutions are not always appropriate to the community and its population. This article aims to describe the technical design of the electrification system of the community of Alto Peru (in the region of Cajamarca, Peru), where the adequate technology was used at each area according to micro-scale resource evaluation and the socioeconomic requirements of the population. Specifically four technologies were implemented: wind microgrids in highlands, a micro-hydro power plant in the presence of a waterfall, a PV microgrid in a group of points sheltered from the wind and individual PV systems in scattered points with low wind potential. This project brought electricity to 58 households, a health center, a school, a church, two restaurants and two shops.Peer ReviewedPostprint (author’s final draft

Comportement rhéologique de nanocomposites à matrice polymère

National audienceDans cette étude, nous avons caractérisé le comportement rhéologique de nanocomposites à base de polypropylène et d'argile lamellaire, compatibilisés avec un polypropylène greffé anhydride maléique. Nous avons étudié l'influence du taux de compatibilisant et du taux d'argile. Le niveau d'exfoliation est quantifié par la valeur du seuil d'écoulement déduit des mesures rhéologiques. Son évolution avec le taux d'argile permet de définir un seuil de percolation de l'ordre de 1,5% en masse

The importance of specific mechanical energy during twin screw extrusion of organoclay based polypropylene nanocomposites

International audienceThis study demonstrates how the specific mechanical energy (SME) can be used to describe the influence of extrusion parameters such as screw rotation speed, feed rate and barrel temperature on clay dispersion in organoclay (OMMT) based polypropylene nanocomposites. These materials were prepared by a melt mixing masterbatch process via twin screw extrusion with a wide range of processing conditions. Maleated polypropylene (PP-g-MA) was used as a compatibilizer to allow clay exfoliation. Characterization of the morphological evolution along the extrusion profile revealed that microscale dispersion primarily happens in the melting zone, whereas continuous exfoliation is observed all along the kneading zones, up to the die exit. The results indicate that exfoliation in the kneading zones is mainly issued from clay tactoids and small aggregates with characteristic size inferior to 10. μm, emphasizing the crucial role of primary microscale dispersion on the final structure and properties of the nanocomposites. Relevant quantitative prediction of the multiscale dispersion state along the extrusion profile was obtained using the melt state SME as unique paramete

Structuration de nanocomposites polyoléfine/argile lamellaire en extrusion bivis corotative

International audienceLa réalisation de nanocomposites par mélange d'argile lamellaire dans une matrice polymère à l'état fondu se fait généralement par extrusion bivis corotative. L'objectif de cette opération est de disperser les agglomérats d'argiles, d'exfolier les feuillets et de distribuer ces charges d'épaisseur nanométrique au sein de la matrice. La forte surface spécifique des argiles permet ainsi de développer largement les interactions polymère/argile. Dans le cas des polyoléfines, un troisième élément doit être ajouté en tant que compatibilisant entre la matrice apolaire et la surface polaire des argiles. Le procédé d'extrusion bivis peut être adapté, selon le résultat recherché, via de nombreux paramètres : profil de vis, vitesse de rotation, débit d'alimentation des doseurs, températures de régulation le long du fourreau. Dans ce travail, nous avons étudié l'effet de ces paramètres procédé sur la structure des nanocomposites aux échelles micrométrique et nanométrique. Une formulation a été choisie en fixant les proportions entre la matrice, le compatibilisant et l'argile. Des échantillons ont été prélevés en sortie de machine et le long des vis pour chaque condition opératoire testée. Le niveau de dispersion de l'argile est évalué en utilisant différentes techniques de caractérisation (MEB, MET, DRX, rhéométrie dynamique). Les résultats montrent que l'augmentation de l'énergie mécanique spécifique (EMS) entraîne une diminution du nombre et de la taille des agglomérats présents au niveau de la microstructure, ainsi qu'un phénomène d'exfoliation plus important au niveau de la nanostructure, jusqu'à atteindre un niveau de saturation de l'état de dispersion de l'argile

Influence of twin-screw processing conditions on structure and properties of polypropylene - Organoclay nanocomposites

International audienceThis study looks at the influence of extrusion parameters such as screw speed, feed rate and barrel temperature on the nanocomposite structure (size of agglomerates, level of intercalation and exfoliation) and its consequences on final mechanical properties. Nanocomposites of polypropylene, maleated polypropylene and organomodified montmorillonite, with respective mass fractions of 85/10/5, were prepared in a co-rotating twin-screw extruder using a masterbatch dilution method. The nanocomposites structure was quantified by scanning and transmission electron microscopy, X-ray diffraction and dynamic rheometry. Relationships between the microstructure at different levels (size and number of agglomerates, interlayer distance, melt yield stress to quantify the exfoliation level) and the processing conditions were established, revealing that specific mechanical energy received during extrusion was the key parameter controlling this microstructure. Mechanical properties in uniaxial tension (apparent Young's modulus) were measured and related to the microstructural parameters resulting from extrusion conditions

A step-by-step guide to assist logistics managers in defining efficient re-shelving solutions for retail store deliveries

Purpose City logistics is a challenge in many cities. Literature works focus on the analysis of large or local-scale solutions to increase the efficiency of freight transport. However, store deliveries from the perspective of practitioners, particularly retail stores, are still an issue. In this context, the purpose of this paper is to propose a decision framework to assist logistics managers in defining efficient re-shelving solutions for store deliveries, according to the emplacement characteristics, city administration constraints and social issues. Design/methodology/approach An iterative step-by-step decision framework is developed, which allows taking decisions in a clear and structured way, including the preferences of key stakeholders. Moreover, a “what if” procedure is proposed, aiming to modify some initial conditions of the target store to achieve more efficient solutions. Findings The proposed decision framework is applicable in practice and helps users (mainly logistics managers) to identify solutions for efficient re-shelving in urban settings. Research limitations/implications The decision framework is applied by the logistics manager of two Spanish food retail stores, but it could be used in different logistics sectors and cities/regions, although adapting the decisions taken at each phase. Practical implications Logistics managers have a support tool when addressing re-shelving solutions for store deliveries. Social implications A balance can be found between company interests (minimise costs) and citizens quality of life (less contamination, noise, traffic, etc.). Originality/value This study simultaneously deals with large- and local-scale decisions faced by logistics managers in their day-to-day activity, considering details about the store location, its surroundings and the company it belongs.Peer ReviewedPostprint (author's final draft

Metodología para el diseño de sistemas de electrificación autónomos para comunidades rurales

Los sistemas de electrificación autónomos basados en el uso de energías renovables son adecuados para electrificar comunidades rurales aisladas. Para su diseño existen herramientas de apoyo a la toma de decisiones, pero no abarcan algunas consideraciones técnicas y sociales, y/o no entran en el detalle específico del proyecto. En este contexto, el objetivo de esta tesis doctoral es desarrollar una metodología para ayudar en el diseño de sistemas de electrificación autónomos basados en las energías eólica y solar, que sea adecuada a las características económicas, técnicas y sociales de comunidades rurales de países en desarrollo, y que considere la opinión de todos los actores involucrados en el proyecto. La metodología de diseño propuesta se divide en 3 etapas principales: - La primera etapa consiste en realizar evaluaciones iniciales (socioeconómica, energética y técnica) para recopilar la información característica de la comunidad a electrificar. - La segunda etapa es el propio proceso de diseño en sí y se divide en 3 niveles de decisión, ordenados en función de la importancia de las decisiones a tomar. En concreto se estudia la influencia sobre el coste de modificaciones en la demanda (nivel 1), la gestión del sistema (nivel 2) y la seguridad del suministro (nivel 3). Cada nivel de decisión se estructura en 2 pasos: primero se generan diversas alternativas de electrificación con un modelo de programación lineal, incluyendo consideraciones técnicas y sociales; y segundo se selecciona la alternativa más adecuada en función de criterios económicos, técnicos y sociales, mediante la técnica multicriterio de la programación compromiso. - La tercera etapa, opcional, permite intentar mejorar el coste de la solución obtenida, manteniendo las decisiones previamente tomadas. Para la validación de este trabajo de investigación, dos expertos en el campo de la electrificación rural han actuado como hipotéticos usuarios de la metodología de diseño, y han realizado todo el proceso para las comunidades reales de El Alumbre y Alto Perú, ambas en Cajamarca (Perú). Se valida, de esta forma, que la metodología propuesta es adecuada para diseñar sistemas de electrificación autónomos. En concreto, permite personalizar la toma de decisiones de forma clara y estructurada, evaluando una gran cantidad de alternativas de electrificación y obteniendo unos resultados que concuerdan con las preferencias del usuario.Autonomous electrification systems based on the use of renewable energies are suitable to electrify isolated rural communities. For its design there are decision-making support tools, but they do not cover some technical and social constraints and do not consider the specific detail of the project. In this context, the aim of this PhD is to develop a methodology for helping to the design of autonomous electrification systems based on wind and solar energies, which is appropriate to the economic, technical and social aspects of rural communities in developing countries, and which considers the views of all stakeholders involved in the project. The proposed design methodology is divided into 3 principal stages: - In the first stage characteristics from the community to electrify are gathered through some initial assessments (socio-economic, resource and technical). - The second stage is the design process itself and is divided into 3 decision levels, ordered according to the importance of the decisions to take. Specifically the influence on the cost of modifications on the demand (level 1), the system management (level 2) and the security of supply (level 3) are studied. Each decision level is divided into 2 steps: first several electrification alternatives are generated through a linear programming model, including technical and social considerations; second the most appropriate alternative is selected based on economic, technical and social criteria, through compromise programming multicriteria technique. - The third stage, optional, allows trying to improve the cost of the obtained solutions, maintaining previously taken decisions. To validate this research work, two experts in the field of rural electrification have acted as hypothetical users of the design methodology, and have carried out all the process for the real communities of El Alumbre and Alto Peru, both in Cajamarca (Peru). Thus, it is validated that the proposed methodology is suitable to design autonomous electrification systems. Specifically, it allows personalizing decision-making in a clear and structured way, evaluating many electrification alternatives and obtaining results that match user’s preferences up

Modelo para el diseño de proyectos de electrificación rural con consideraciones técnicas y sociales

En la casi totalidad de los países del mundo, la estrategia más utilizada para dar acceso a la electricidad es la extensión de la red eléctrica. Sin embargo, esta estrategia es poco factible cuando se trata de llegar a zonas alejadas, de difícil acceso y con baja densidad de población. Una buena alternativa, son los sistemas autónomos y descentralizados, basados en energías renovables. Los sistemas eólicos y fotovoltaicos son una de las opciones técnicas posibles. Para diseñar estos sistemas, existen modelos matemáticos que consideran criterios técnicos y económicos pero se ha visto que es necesario incorporar criterios sociales para facilitar la integración de los sistemas de electrificación en el día a día de los beneficiarios. Este trabajo tiene como objetivo analizar las características sociales a incluir, incorporar éstas en los modelos matemáticos y estudiar la influencia de cada una sobre las soluciones de electrificación. Con este trabajo se obtiene un modelo matemático de programación lineal entera y mixta que minimiza costes a la vez que cumple con las exigencias técnicas de los equipos e incorpora consideraciones sociales para mejorar la calidad y la seguridad del suministro energético así como facilitar la gestión de los sistemas de electrificación. Para ello, en primer lugar se analizan problemas sociales hallados en diferentes experiencias de electrificación y se determinan posibles soluciones o mejoras. En segundo lugar, se proponen y validan distintas modelizaciones para cada mejora, con el objetivo determinar la modelización más eficiente e incorporarla a los modelos. Finalmente, en tercer lugar, se estudia la influencia de cada mejora sobre las soluciones de electrificación, para comprobar el aporte de cada una al bienestar social de las comunidades. La experimentación se valida en 5 comunidades de la sierra andina peruana (Cajamarca, Perú); 3 de ellas ya electrificadas (El Alumbre, Alto Perú parte carretera y Campo Alegre) y 2 por electrificar (Alto Perú parte Norte y Alto Perú parte Sur). Como resultado de la experimentación, las mejoras sociales aportadas en este trabajo logran generar sistemas de electrificación que mejoran la seguridad del suministro energético y facilitan la gestión de los sistemas de electrificación, con unos incrementos de coste muy pequeños