Market perspectives of stationary fuel cells in a sustainable energy supply system—long-term scenarios for Germany

Because of high efficiency, low environmental impacts and a potential role in transforming our energy system into a hydrogen economy, fuel cells are often considered as a key technology for a sustainable energy supply. However, the future framing conditions under which stationary fuel cells have to prove their technical and economic competitiveness are most likely characterised by a reduced demand for space heating, and a growing contribution of renewable energy sources to heat and electricity supply, which both directly limit the potential for combined heat and power generation, and thus also for fuel cells. Taking Germany as a case study, this paper explores the market potential of stationary fuel cells under the structural changes of the energy demand and supply system required to achieve a sustainable energy supply. Results indicate that among the scenarios analysed it is in particular a strategy oriented towards ambitious CO₂-reduction targets, which due to its changes in the supply structure is in a position to mobilise a market potential that might be large enough for a successful fuel cell commercialisation. However, under the conditions of a business-as-usual trajectory the sales targets of fuel cell manufacturers cannot be met.     

27-GHz bandwidth high-speed monolithic integrated optoelectronicphotoreceiver consisting of a waveguide fed photodiode and anInAlAs/InGaAs-HFET traveling wave amplifier

A monolithic integrated photoreceiver for 1.55-μm wavelength has been designed for operation in a 20-Gb/s synchronous digital hierarchy system (SDH/SONET), based on a new integration concept. The optoelectronic integrated circuit (OEIC) receiver combines a waveguide-integrated PIN-photodiode and a traveling wave amplifier in coplanar waveguide layout with four InAlAs/InGaAs/InP-HFETs (0.7-μm gate length). The receiver demonstrates a bandwidth of 27 GHz with a low frequency transimpedance of 40 dBΩ. This is, to our knowledge, the highest bandwidth ever reported for a monolithic integrated photoreceiver on InP. Furthermore, a receiver sensitivity of -12 dBm in the fiber (20 Gb/s, BER=10^-9) and an overall optical input dynamic range of 27 dB is achieved. Optical time domain multiplex (TDM) system experiments of the receiver packaged in a module show an excellently shaped eye pattern for 20 Gb/s and an overall sensitivity of -30.5 dBm (BER=10^-9) [including erbium doped fiber amplifiers (EDFA)]     

Comparison of psychodiagnostic methods for dementia and deterioration

Several cognitive impairment/dementia diagnostic methods were examined concerning their results: (a) in the differentiation of accidental and pathological ability changes; (b) in the demonstration/exclusion of cognitive impairment; and (c) the degree of dementia. Sixty-five patients suffering from brain damage were examined with five accepted methods of diagnosing dementia (Syndrom-kurztest, KAI-MWT-Methode, Demenz-Test, Mini-Mental-Status-Test, Wurzer-Methode) and a comprehensive performance test battery as an external criterion for valid determination of the degree of dementia and definite differentiation of accidental and pathological performance changes. The five methods of diagnosing dementia differ appreciably in determining the degree of severity (r = 0.44). They are effective in registering accidental performance changes in comparison with the outer criterion, but pathological changes are inaccurately registered (hit rate 88%/53%); the results concerning the degree of cognitive impairment are identical: between 25 and 43% (r = 0.43). High rates (58%) of false-negative diagnoses are especially apparent in the range of slight and intermediate cognitive impairment. The methods examined are only useful for the demonstration and not for the exclusion of severe cognitive impairment (dementia) and in no circumstances for the registration of slight/intermediate cognitive impairment. Valid diagnosis of cognitive impairment/dementia necessitates the use of test batteries that differentiate functions including the premorbid performance level.     

Statistical Modeling of Fetal Heart Rate Variability

The random variability of fetal heart rate (FHR) is of practical importance in obstetric management. The variability is not white, however, and cannot be adequately described by its variance alone. We have modeled FHR variability as the scalar output of a multivariate, nonlinear stochastic process. An adaptation of the Kalman filter algorithm is used as part of an approximate maximum likelihood estimator of the process parameters. The filter algorithm permits recording artifacts to be disregarded, by treating them as "missing" observations.     

Existence range,structural and dielectric properties of ZrxTiySnzO4 ceramics (x+y+z=2)

Ceramic samples in the system ZrO₂TiO₂SnO₂ were prepared in order to investigate the existence range of a homogeneous phase Zr_xTi_ySn_zO₄ with x+y+z=2. Lattice parameters, dielectric properties and thermal expansion were determined. A homogeneous solid solution phase was found in part of the composition diagram. Its crystal structure is isomorphous with ZrTiO₄. The unusual variation of the lattice parameters with the Sn content is discussed and the range of compositions suitable for dielectric resonators is defined.     

Generation of geometrically and radiometrically terrain corrected SAR image products

Terrain undulations affect the geometric and radiometric quality of synthetic aperture radar images. The correction of these effects becomes indispensable when quantitative image analysis is performed with respect to the derivation of geo- and biophysical parameters. The paper presents a rigorous approach for geometric and radiometric correction of SAR images. Using a digital elevation model, the imaging geometry is reconstructed and is used to perform geometric and radiometric correction of terrain induced distortions. The importance of a stringent radiometric correction based on the integration of the image brightness is emphasized. The approach guarantees that the energy contained in the image data is preserved throughout the geocoding process. The resulting backscattering images are fully terrain corrected and can be used for further quantitative investigations and may also improve qualitative studies as e.g. land cover classifications. The technique is applicable for different sensor types and image products, including already geocoded SAR images. The effect of different resolutions of digital elevation models used for the correction of the backscattering coefficient is investigated.     

Junction formation of CuInSe2 with CdS: A comparative study of “dry” and “wet” interfaces

The junction formation of polycrystalline CuInSe₂ absorbers (CIS) with thermally evaporated CdS was investigated by high-resolution synchrotron X-ray photoelectron spectroscopy. The chemistry and electronics of the interfaces of Cd partial electrolyte treated CIS (“wet” processed) and clean, decapped CIS (“dry” processed) were compared. A valence band offset of 0.96(10) eV was determined in both cases. The Cd(Se,OH) surface layer induced by the wet Cd partial electrolyte process does not significantly modify the band alignment at the CIS/CdS heterointerface from the “dry”, vacuum-processed CIS/CdS interface.During the stepwise interface formation the energy converting capability of the CIS/CdS heterojunction was assessed by in situ surface photovoltage measurements at room temperature. The evolution of the surface photovoltage significantly differs for the “wet” and the “dry” interfaces and is discussed in relation to the function in solar cell devices.     

Response of high performance concrete plates to impact of non-deforming projectiles

The relatively recent technology, which enables the production of high strength concrete (HSC), makes HSC a prospective material for the construction of impact-resisting barriers. However, current penetration formulae are based on test data of normal strength concrete (NSC) and their extrapolation to higher concrete strengths is unsafe. The response of 80×80 cm high performance concrete (HPC) plate specimens to an impact of non-deforming steel projectiles was examined in an experimental study. The tests were planned with an aim to observe the influence of the concrete mix ingredients and amount and type of reinforcement on the performance of HSC under this type of loading. The variants that were examined were the aggregates (different types and maximum size), addition of micro-silica (MS) and steel fibers, and reinforcement details. The main findings show that design of HPC barriers to withstand impact loads involves several aspects. These are aimed at achieving enhanced properties of the structural element, where only one of which is the concrete's compressive strength.     

OctoMap: an efficient probabilistic 3D mapping framework based on octrees

Three-dimensional models provide a volumetric representation of space which is important for a variety of robotic applications including flying robots and robots that are equipped with manipulators. In this paper, we present an open-source framework to generate volumetric 3D environment models. Our mapping approach is based on octrees and uses probabilistic occupancy estimation. It explicitly represents not only occupied space, but also free and unknown areas. Furthermore, we propose an octree map compression method that keeps the 3D models compact. Our framework is available as an open-source C++ library and has already been successfully applied in several robotics projects. We present a series of experimental results carried out with real robots and on publicly available real-world datasets. The results demonstrate that our approach is able to update the representation efficiently and models the data consistently while keeping the memory requirement at a minimum.