975 research outputs found

    From National Hierarchies to International Standardization: Historical and Modal Changes in the Coordination of Telecommunications

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    Die Konvergenz von Telekommunikation und Datenverarbeitung hat eine globale Expansion von Netzen und Diensten ausgelöst, die von einer Deregulierung des Sektors begleitet wurde. Eine Vielzahl heterogener Akteure auf dem Weltmarkt muß die jeweiligen Entwicklungs- und Produktionsaktivitäten ebenso wie das Angebot neuer Dienste koordinieren. Der alte Modus hierarchischer Koordination, der technische, ökonomische und politische Steuerung internalisierte und sich in der Ära souveräner Nationalstaaten früherer Jahrzehnte etablierte, ließ sich nicht in eine transnationale Hierarchie transformieren. Koordination beschränkt sich daher auf die Herstellung technischer Kompatibilität von Systemen der Telekommunikation. Es hat sich ein Netz internationaler und regionaler Standardisierungsgremien herausgebildet, das ständig größer wird. Diese Gremien erarbeiten die benötigten Empfehlungen, die eher optional und komplementär als substitutiv sind, was eine Arbeitsteilung anstelle von Konkurrenz begünstigt hat.The convergence of telecommunications and computer technology stimulated a global expansion of networks and services which was accompanied by a deregulation of this industry. In the liberalized worldmarket a great number of heterogeneous actors must coordinate the development and production of technology as well as the provision of new services. The old mode of hierarchical coordination internalizing technical, economic and political control, which originated from the sovereign state system of earlier decades, could not be transformed into transnational hierarchy. Thus coordination is widely restricted to achieving technical compatibility of telecommunications systems. A network of international and regional standardization committees, growing in number, has evolved. They issue the required technical recommendations, which are usually more complementary and optional than substitutive, so that division of labor instead of competition prevails.Abstract 1 Introduction 2 Large Technical Systems in National Containment: The Old Order in Telecommunications 3 From National Isolation to Minimal International Coordination 3.1 Modes of International Coordination: Some Theoretical Considerations 3.2 The Long Road to Little International Coordination 4 Trans-border Expansion of Telecommunications and the Erosion of the Old Order 5 Technical Systems' Compatibility Requirements and the Proliferation of International Standardization 5.1 Basic Problems of International Standardization Procedures 5.2 The Proliferation of International Standardization Organizations 6 Conclusion Bibliograph

    Laser-based isotope ratio analyzers: the user perspective

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    Can a bog drained for forestry be a stronger carbon sink than a natural bog forest?

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    This study compares the CO2 exchange of a natural bog forest, and of a bog drained for forestry in the pre-Alpine region of southern Germany. The sites are separated by only 10 km, they share the same soil formation history and are exposed to the same climate and weather conditions. In contrast, they differ in land use history: at the Schechenfilz site a natural bog-pine forest (Pinus mugo ssp. rotundata) grows on an undisturbed, about 5 m thick peat layer; at Mooseurach a planted spruce forest (Picea abies) grows on drained and degraded peat (3.4 m). The net ecosystem exchange of CO2 (NEE) at both sites has been investigated for 2 years (July 2010-June 2012), using the eddy covariance technique. Our results indicate that the drained, forested bog at Mooseurach is a much stronger carbon dioxide sink (-130 ± 31 and -300 ± 66 g C m-2 a-1 in the first and second year, respectively) than the natural bog forest at Schechenfilz (-53 ± 28 and -73 ± 38 g C m-2 a-1). The strong net CO2 uptake can be explained by the high gross primary productivity of the 44-year old spruces that over-compensates the two-times stronger ecosystem respiration at the drained site. The larger productivity of the spruces can be clearly attributed to the larger plant area index (PAI) of the spruce site. However, even though current flux measurements indicate strong CO2 uptake of the drained spruce forest, the site is a strong net CO2 source when the whole life-cycle since forest planting is considered. It is important to access this result in terms of the long-term biome balance. To do so, we used historical data to estimate the difference between carbon fixation by the spruces and the carbon loss from the peat due to drainage since forest planting. This rough estimate indicates a strong carbon release of +134 t C ha-1 within the last 44 years. Thus, the spruces would need to grow for another 100 years at about the current rate, to compensate the potential peat loss of the former years. In contrast, the natural bog-pine ecosystem has likely been a small but stable carbon sink for decades, which our results suggest is very robust regarding short-term changes of environmental factors

    Angewandte Spektroskopie mit Halbleiterlasern

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    Exact Self-consistent Particle-like Solutions to the Equations of Nonlinear Scalar Electrodynamics in General Relativity

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    Exact self-consistent particle-like solutions with spherical and/or cylindrical symmetry to the equations governing the interacting system of scalar, electromagnetic and gravitational fields have been obtained. As a particular case it is shown that the equations of motion admit a special kind of solutions with sharp boundary known as droplets. For these solutions, the physical fields vanish and the space-time is flat outside of the critical sphere or cylinder. Therefore, the mass and the electric charge of these configurations are zero.Comment: 17 pages, Submitted to the International Journal of Theoretical Physic

    Can a bog drained for forestry be a stronger carbon sink than a natural bog forest?

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    This study compares the CO2 exchange of a natural bog forest, and of a bog drained for forestry in the pre-Alpine region of southern Germany. The sites are separated by only 10 km, they share the same soil formation history and are exposed to the same climate and weather conditions. In contrast, they differ in land use history: at the Schechenfilz site a natural bog-pine forest (Pinus mugo ssp. rotundata) grows on an undisturbed, about 5 m thick peat layer; at Mooseurach a planted spruce forest (Picea abies) grows on drained and degraded peat (3.4 m). The net ecosystem exchange of CO2 (NEE) at both sites has been investigated for 2 years (July 2010-June 2012), using the eddy covariance technique. Our results indicate that the drained, forested bog at Mooseurach is a much stronger carbon dioxide sink (-130 ± 31 and -300 ± 66 g C m-2 a-1 in the first and second year, respectively) than the natural bog forest at Schechenfilz (-53 ± 28 and -73 ± 38 g C m-2 a-1). The strong net CO2 uptake can be explained by the high gross primary productivity of the 44-year old spruces that over-compensates the two-times stronger ecosystem respiration at the drained site. The larger productivity of the spruces can be clearly attributed to the larger plant area index (PAI) of the spruce site. However, even though current flux measurements indicate strong CO2 uptake of the drained spruce forest, the site is a strong net CO2 source when the whole life-cycle since forest planting is considered. It is important to access this result in terms of the long-term biome balance. To do so, we used historical data to estimate the difference between carbon fixation by the spruces and the carbon loss from the peat due to drainage since forest planting. This rough estimate indicates a strong carbon release of +134 t C ha-1 within the last 44 years. Thus, the spruces would need to grow for another 100 years at about the current rate, to compensate the potential peat loss of the former years. In contrast, the natural bog-pine ecosystem has likely been a small but stable carbon sink for decades, which our results suggest is very robust regarding short-term changes of environmental factors

    Temas Velados del Romancero Gitano de Federico Garcia Lorca

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    LUX -- A Laser-Plasma Driven Undulator Beamline

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    The LUX beamline is a novel type of laser-plasma accelerator. Building on the joint expertise of the University of Hamburg and DESY the beamline was carefully designed to combine state-of-the-art expertise in laser-plasma acceleration with the latest advances in accelerator technology and beam diagnostics. LUX introduces a paradigm change moving from single-shot demonstration experiments towards available, stable and controllable accelerator operation. Here, we discuss the general design concepts of LUX and present first critical milestones that have recently been achieved, including the generation of electron beams at the repetition rate of up to 5 Hz with energies above 600 MeV and the generation of spontaneous undulator radiation at a wavelength well below 9 nm.Comment: submitte

    Maghemite Nanofluid Based on Natural Ester: Cooling and Insulation Properties Assessment

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    The objective of this work is to study the effect that the addition of magnetic nanoparticles to a natural ester has on its properties and its cooling capacity. Some samples of ferrofluid (natural ester with maghemite) have been prepared using different concentrations. These have been characterized by measuring their thermo-hydraulic and dielectric properties, to find an optimal concentration. Then, the cooling capacities of the optimal nanofluid and the base fluid have been tested in a transformer immersed in these liquids. The experimental platform allowed the measurement of temperatures in different locations at different load levels. Parallel simulations of these tests have been carried out with a Computational Fluid Dynamics model of the experimental platform. The results show an improvement of the insulating capacity of the base fluid with the addition of maghemite nanoparticles, and an enhanced cooling capacity.
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