5,022 research outputs found

    Global value chains during the great trade collapse: a bullwhip effect?

    Get PDF
    This paper analyzes the performance of global value chains during the trade collapse. To do so, it exploits a unique transaction-level dataset on French firms containing information on cross-border monthly transactions matched with data on worldwide intra-firm linkages as defined by property rights (multinational business groups, hierarchies of firms). This newly assembled dataset allows us to distinguish firm-level transactions among two alternative organizational modes of global value chains: internalization of activities (intra-group trade/trade among related parties) or establishment of supply contracts (arm's length trade/trade among unrelated parties). After an overall assessment of the role of global value chains during the trade collapse, we document that intra-group trade in intermediates was characterized by a faster drop followed by a faster recovery than arm's length trade. Amplified fluctuations in terms of trade elasticities by value chains have been referred to as the "bullwhip effect" and have been attributed to the adjustment of inventories within supply chains. In this paper we first confirm the existence of such an effect due to trade in intermediates, and we underline the role that different organizational modes can play in driving this adjustment. JEL Classification: F23, F15, L22.Trade collapse, multinational firms, global value chains, hierarchies of firms , vertical integration.

    The Potential of Smart Glazing for Occupant Well-Being and Reduced Energy Load in a Central-Mediterranean Climate

    Get PDF
    The ever-increasing aesthetically driven demand for fully glazed façades poses a design challenge; not least in controlling the cooling demand and occupant well-being of such buildings, especially in a central Mediterranean climate. This paper outlines the ever-important need to design for occupants and for designers to keep in mind, first and foremost, occupant well-being rather than aim solely to create energy-efficient buildings. The original objective of buildings was to provide shelter. Today however, the need for occupant comfort and its direct effect on productivity cannot be ignored. This need, therefore, ought to feature a central role in any building design. Studies show that occupant well-being is directly related to a range of environmental factors, particularly daylight distribution, glare and indoor air temperature. The use of external shading devices and more commonly, indoor blinds are often the adopted approaches to attempt to achieve indoor occupant comfort, often to the detriment of views. Adaptive facades seek to address the need to somehow strike a balance between occupant comfort and energy efficiency. These facades range from exterior and interior shading devices with varying control strategies, to the different forms of adaptive/switchable glazing technologies intended to control the visual light transmittance and solar radiation transmitted into a building’s interior. In the opinion of the authors, electrochromic glazing has a great potential in a cooling-dominated central Mediterranean climate, to achieve a compromise between occupant visual and thermal comfort whilst retaining unobstructed outdoor views at all times. Research shows that the potential benefits of electrochromic glazing have not yet been studied enough in real-life scenarios,and this paper further introduces the objectives for field study within two identical offices, having a South-South-East orientation, located in a central Mediterranean climate

    Global Value Chains During the Great Trade Collapse: A Bullwhip Effect?

    Get PDF
    This paper analyzes the performance of global value chains during the trade collapse. To do so, it exploits a unique transaction-level dataset on French firms containing information on cross-border monthly transactions matched with data on worldwide intra-.rm linkages as defined by property rights (multinational business groups, hierarchies of firms). This newly assembled dataset allows us to distinguish firm-level transactions among two alternative organizational modes of global value chains: internalization of activities (intra- group trade/trade among related parties) or establishment of supply contracts (arm's length trade/trade among unrelated parties). After an overall assessment of the role of global value chains during the trade collapse, we document that intra-group trade in intermediates was characterized by a faster drop followed by a faster recovery than arm's length trade. Amplified fluctuations in terms of trade elasticities by value chains have been referred to as the "bullwhip effect" and have been attributed to the adjustment of inventories within supply chains. In this paper we first con.rm the existence of such an effect due to trade in inter- mediates, and we underline the role that different organizational modes can play in driving this adjustment.trade collapse, multinational firms, global value chains, hierarchies of firms, vertical integration

    In Pursuit of Aviation Cybersecurity: Experiences and Lessons From a Competitive Approach

    Get PDF
    The passive and independent localization of aircraft has been the subject of much cyberphysical security research. We designed a multistage open competition focusing on the offline batch localization problem using opportunistic data sources. We discuss setup, results, and lessons learned

    The potential of smart glazing for occupant well-being and reduced energy load in a Central-Mediterranean climate

    Get PDF
    The ever-increasing aesthetically driven demand for fully glazed façades poses a design challenge; not least in controlling the cooling demand and occupant well-being of such buildings, especially in a central Mediterranean climate. This paper outlines the ever-important need to design for occupants and for designers to keep in mind, first and foremost, occupant well-being rather than aim solely to create energyefficient buildings. The original objective of buildings was to provide shelter. Today however, the need for occupant comfort and its direct effect on productivity cannot be ignored. This need, therefore, ought to feature a central role in any building design. Studies show that occupant well-being is directly related to a range of environmental factors, particularly daylight distribution, glare and indoor air temperature. The use of external shading devices and more commonly, indoor blinds are often the adopted approaches to attempt to achieve indoor occupant comfort, often to the detriment of views. Adaptive facades seek to address the need to somehow strike a balance between occupant comfort and energy efficiency. These facades range from exterior and interior shading devices with varying control strategies, to the different forms of adaptive/switchable glazing technologies intended to control the visual light transmittance and solar radiation transmitted into a building's interior. In the opinion of the authors, electrochromic glazing has a great potential in a cooling-dominated central Mediterranean climate, to achieve a compromise between occupant visual and thermal comfort whilst retaining unobstructed outdoor views at all times. Research shows that the potential benefits of electrochromic glazing have not yet been studied enough in real-life scenarios, and this paper further introduces the objectives for a field study within two identical offices, having a South-South-East orientation, located in a central Mediterranean climate.peer-reviewe

    Interface-driven phase separation in multifunctional materials: the case of GeMn ferromagnetic semiconductor

    Get PDF
    We use extensive first principle simulations to show the major role played by interfaces in the mechanism of phase separation observed in semiconductor multifunctional materials. We make an analogy with the precipitation sequence observed in over-saturated AlCu alloys, and replace the Guinier-Preston zones in this new context. A new class of materials, the α\alpha phases, is proposed to understand the formation of the coherent precipitates observed in the GeMn system. The interplay between formation and interface energies is analyzed for these phases and for the structures usually considered in the literature. The existence of the alpha phases is assessed with both theoretical and experimental arguments

    Factors driving the biogeochemical budget of the Amazon River and its statistical modelling Facteurs denext term contrôle du bilan biogéochimique previous termdenext term l'Amazone et modélisation statistique associée

    Get PDF
    International audienceThe seasonal and interannual fluctuations of the biogeochemical budget (solutes, suspended matter, isotopes) of the Amazon River basin were analyzed, with a special focus on 44 physicochemical parameters monitored over the period 1982-1984 during the Carbon in the AMazon River Experiment (CAMREX) project. The relevant factors driving this variability were identified and sorted through the implementation of a statistical-regressive model coupled to variance analysis. Basically, the compositional fluctuations in the Amazon River are related (1) to the variable contribution of major tributaries (variable regional source) to the river flow but also (2) to the variable contribution of hydrological sources, (3) to river processes, i.e. in-stream diagenesis and sediment dynamics and (4) to the hydrological budget of the floodplains. Their respective contributions to the variability of chemical signals observed in the stream waters depend on which parameter was investigated but their combination explains on average 85% of the observed variability. The variability related to regional sources was captured by the compared measures of flow discharge and biogeochemical fluxes at the outlet of the major tributaries. The variability of hydrological sources was described by the variable contribution of three runoffs of distinct but constant composition: forwarded direct runoff, delayed floodplain runoff and baseflow. Several methods were tested to depict the seasonal and interannual variations of their individual discharges. Biologically-mediated processes were related to a hydrobiological index IBIO = [O2]-[CO2] which allows tracking the nature of the dominant ecological regime (autotrophy vs. heterotrophy). The alteration of chemical signals related to the intermittent discharge of the floodplains (where specific processes occur such as: gas exchanges at the air-water interface, sorption of dissolved organic matter, chemical weathering, deposition vs. remobilization of sediments, etc.) was simulated by taking into account the default of hydrological balance between inflows and outflows, used as a marker of floodplains discharge. This analysis shows that the chemical baseline observed in the waters of the Amazon River is mostly acquired upstream from the junction of major tributaries with the Amazon main reach. Les fluctuations saisonnières et interannuelles du bilan biogéochimique (solutés, matière particulaire, isotopes) du fleuve Amazone ont été analysées, avec une attention particulière apportée à 44 paramètres physicochimiques mesurés entre 1982 et 1984 dans le cadre du programme CAMREX. Les facteurs exerçant une influence significative sur cette variabilité ont été identifiés et hiérarchisés par le biais d'un modèle statistique couplé à une analyse previous termdenext term variance. Les variations previous termdenext term composition des eaux previous termdenext term l'Amazone sont fondamentalement associées (1) à previous termlanext term contribution variable previous termdenext term ses affluents majeurs (source régionale variable) au débit total, mais aussi (2) à previous termlanext term contribution variable des pôles previous termdenext term mélange hydrologiques, (3) à des processus fluviaux correspondant au régime hydrobiologique et à previous termlanext term dynamique sédimentaire et (4) au bilan hydrologique des plaines d'inondation. Leurs contributions respectives à previous termlanext term variabilité des signaux chimiques observés dans les eaux du fleuve dépendent du paramètre considéré, mais leur combinaison explique en moyenne 85 % previous termde lanext term variabilité observée. previous termLanext term variabilité associée aux contributions régionales variables est appréhendée en procédant aux bilans entrées-sorties des débits et flux biogéochimiques. previous termLanext term variabilité previous termdenext term contribution des pôles previous termdenext term mélange est décrite par previous termlanext term contribution variable previous termdenext term trois écoulements previous termdenext term compositions distinctes mais constantes : l'écoulement direct à expression précoce, l'écoulement local previous termdenext term vidange alluviale à expression différée et l'écoulement previous termdenext term base. Douze méthodes ont été testées afin previous termdenext term décrire les variations saisonnières et interannuelles des débits individuels previous termdenext term chaque pôle previous termdenext term mélange. Les processus contrôlés par le vivant sont appréhendés à partir d'un indice hydrobiologique IBIO = [O2]-[CO2] qui permet previous termdenext term déterminer previous termlanext term nature du régime hydro-écologique dominant (autotrophe vs. hétérotrophe). L'altération des signaux chimiques générée par previous termlanext term vidange intermittente des plaines d'inondation (au niveau desquelles ont lieu des processus spécifiques : échanges gazeux, sorption previous termdenext term matière organique dissoute, érosion chimique, dépôt vs. remise en suspension previous termdenext term sédiments, etc.) est simulée en prenant en compte le défaut previous termdenext term bilan hydrologique entrées-sorties utilisé comme marqueur previous termdenext term débit des plaines d'inondation. Cette analyse montre que le bruit previous termdenext term fond chimique observé dans les eaux du fleuve Amazone est principalement acquis en amont des confluences entre le tronçon fluvial étudié et les principaux affluents qui l'alimentent
    corecore