The European employment strategy in an enlarged EU

"This article reviews the origins, development and impact of the European Employment Strategy against the backdrop of the employment performances and policies of the EU, from the early 1990s up to the mid-term review of the Lisbon Strategy in 2005. It recalls how the issue of employment was put at the centre of the policy debate in the 1990s and of the discussion about the right balance between economic and social policy integration at EU level. While the EU-wide emphasis on employment initiated in the mid-1990s is likely to have had some positive effects, in particular in terms of a return to employment growth and an increase in participation and employment rates, many major challenges remain or have developed in the meantime. The experience of the EES shows that there is room for a European strategy to promote growth and jobs." (Author's abstract, IAB-Doku) ((en))Beschäftigungspolitik - historische Entwicklung, Beschäftigungspolitik, politischer Entscheidungsprozess, politischer Wandel, Beschäftigungsentwicklung, Arbeitsmarktentwicklung, Produktivitätsentwicklung, Wirtschaftsentwicklung, Europäische Union

Modeling of Subsurface Scattering from Ice Sheets for Pol-InSAR Applications

Remote sensing is a fundamental tool to measure the dynamics of ice sheets and provides valuable information for ice sheet projections under a changing climate. There is, however, the potential to further reduce the uncertainties in these projections by developing innovative remote sensing methods. One of these remote sensing techniques, the polarimetric synthetic aperture radar interferometry (Pol-InSAR), is known since decades to have the potential to assess the geophysical properties below the surface of ice sheets, because of the penetration of microwave signals into dry snow, firn, and ice. Despite this, only very few studies have addressed this topic and the development of robust Pol-InSAR applications is at an early stage. Two potential Pol-InSAR applications are identified as the motivation for this thesis. First, the estimation and compensation of the penetration bias in digital elevation models derived with SAR interferometry. This bias can lead to errors of several meters or even tens of meters in surface elevation measurements. Second, the estimation of geophysical properties of the subsurface of glaciers and ice sheets using Pol-InSAR techniques. There is indeed potential to derive information about melt-refreeze processes within the firn, which are related to density and affect the mass balance. Such Pol-InSAR applications can be a valuable information source with the potential for monthly ice sheet wide coverage and high spatial resolution provided by the next generation of SAR satellites. However, the required models to link the Pol-InSAR measurements to the subsurface properties are not yet established. The aim of this thesis is to improve the modeling of the vertical backscattering distribution in the subsurface of ice sheets and its effect on polarimetric interferometric SAR measurements at different frequencies. In order to achieve this, polarimetric interferometric multi-baseline SAR data at different frequencies and from two different test sites on the Greenland ice sheet are investigated. This thesis contributes with three concepts to a better understanding and to a more accurate modeling of the vertical backscattering distribution in the subsurface of ice sheets. First, the integration of scattering from distinct subsurface layers. These are formed by refrozen melt water in the upper percolation zone and cause an interesting coherence undulation pattern, which cannot be explained with previously existing models. This represents a first link between Pol-InSAR data and geophysical subsurface properties. The second step is the improved modeling of the general vertical backscattering distribution of the subsurface volume. The advantages of more flexible volume models are demonstrated, but interestingly, the simple modification of a previously existing model with a vertical shift parameter lead to the best agreement between model and data. The third contribution is the model based compensation of the penetration bias, which is experimentally validated. At the investigated test sites, it becomes evident that the model based estimates of the surface elevations are more accurate than the interferometric phase center locations, which are conventionally used to derive surface elevations of ice sheets. This thesis therefore improves the state of the art of subsurface scattering modeling for Pol-InSAR applications, demonstrates the model-based penetration bias compensation, and makes a further research step towards the retrieval of geophysical subsurface information with Pol-InSAR

Ecology, biogeography and responses to habitat degradation of a highly diverse rainforest ant community and taxonomy of Afrotropical Pheidole Westwood (Hymenoptera, Formicidae)

This thesis is about the Kakamega Forest ant fauna in Kenya. With currently 329 ant species the region is the most diverse ever sampled in Africa and, in terms of altitude and biogeographic distribution, probably also one of the most interesting. Ecologically, the ants of the Kakamega Forest showed high associations between three different niche variables (habitat, microhabitat and foraging). The distribution of most species also showed associations with their habitat and microhabitat use. Furthermore, ant species diversity and their ecological functions decreased with an increase in habitat degradation from forest to farmland habitats. In order to describe some of the new species found in the Afrotropical rainforests, a taxonomic treatment of the hyperdiverse genus Pheidole was included in this thesis. Therein, several new species groups were defined and seven new species were described in a systematic revision of the Pheidole pulchella group

Scalable and Energy-Efficient Millimeter Massive MIMO Architectures: Reflect-Array and Transmit-Array Antennas

Hybrid analog-digital architectures are considered as promising candidates for implementing millimeter wave (mmWave) massive multiple-input multiple-output (MIMO) systems since they enable a considerable reduction of the required number of costly radio frequency (RF) chains by moving some of the signal processing operations into the analog domain. However, the analog feed network, comprising RF dividers, combiners, phase shifters, and line connections, of hybrid MIMO architectures is not scalable due to its prohibitively high power consumption for large numbers of transmit antennas. Motivated by this limitation, in this paper, we study novel massive MIMO architectures, namely reflect-array (RA) and transmit-array (TA) antennas. We show that the precoders for RA and TA antennas have to meet different constraints compared to those for conventional MIMO architectures. Taking these constraints into account and exploiting the sparsity of mmWave channels, we design an efficient precoder for RA and TA antennas based on the orthogonal matching pursuit algorithm. Furthermore, in order to fairly compare the performance of RA and TA antennas with conventional fully-digital and hybrid MIMO architectures, we develop a unified power consumption model. Our simulation results show that unlike conventional MIMO architectures, RA and TA antennas are highly energy efficient and fully scalable in terms of the number of transmit antennas.Comment: submitted to IEEE ICC 201