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排序方式: 共有833条查询结果,搜索用时 31 毫秒
71.
Christine Bratrich Bernhard Truffer Klaus Jorde Jochen Markard Werner Meier Armin Peter Matthias Schneider Bernhard Wehrli 《河流研究与利用》2004,20(7):865-882
Hydropower is the most important renewable electricity source worldwide. It shows clear advantages for the global CO2 balance but creates serious ecological impacts on a local scale. As a consequence, concern for the conservation of natural river ecosystems is growing within society and more people are willing to pay extra for so‐called ‘green electricity’. The definition of ‘green’, however, is not straightforward and customers cannot directly examine the quality of electricity products. Therefore, credible certification of high ecological standards is essential for successful green electricity marketing. In this paper we introduce a new assessment procedure for evaluating environmentally compatible hydropower production. This so‐called ‘Green Hydro’ concept was developed in the context of a multidisciplinary case study on a 400 MW hydropower scheme in the Southern Alps of Switzerland. The concept guarantees both general standards for different schemes operating in different types of watersheds and flexibility for local particularities. We developed an environmental management matrix that considers basic criteria and eco‐investments and covers five environmental areas of concern (i.e. hydrological character, connectivity, morphology, landscape, and biological communities). The ecological perspective is complemented by five management domains (i.e. instream flow regimes, hydropeaking, reservoir and bedload management, and power plant structures). Applying assessment and modelling tools for the Green Hydro procedure showed that dynamic habitat models allowed quantification of the effects of different instream flow regulations at morphologically distinct sites. In this case, morphological restoration could be more beneficial than increasing the minimum flow. The first experience with the Green Hydro certification is encouraging. So far, 13 facilities have successfully passed the certification procedure. They produce a total of 186 GWh green electricity per year, which is sufficient for the supply of almost 40 000 households in Switzerland. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
72.
Armin De Meijere Klaus Michelsen Rolf Gleiter Jens Spanget-Larsen 《Israel journal of chemistry》1989,29(2-3):153-164
The syntheses of the new hydrocarbons trimethylenetriasterane 12 , trispirocyclopropanetriasterane 3 , trispirocyclopropanenortricyclane 4 , and of the trispirocyclopropanenorbornanes 5, 6 , and 7 are reported. 12 contains six vinylcyclopropane units rigidly held in an antiperiplanar (ap) conformation in a D3h symmetric framework. 3 and 4 are the first model compounds with bicyclopropyl units rigidly fixed in an s-trans (ap) conformation (Θ = 180°). Their PE spectra reveal that the interaction parameter βww = −1.73 eV for this arrangement is the same as that for Θ = 0°. 相似文献
73.
74.
75.
In this work, commercially available white paint is applied as a pigmented diffuse reflector (PDR) on the rear surface of thin-film crystalline silicon (c-Si) solar cells with a silicon thickness in the 1–2 μm range. We show that white paint increases the short-circuit current density of the solar cells enormously, with a boost of 41% observed for very thin planar solar cells illuminated with the global AM1.5 solar spectrum. We also show that white paint is a better back surface reflector (BSR) than aluminium, air, a transparent conductive oxide (TCO)/aluminium stack, and even a detached aluminium mirror. While previous studies have investigated the influence of PDRs on silicon solar cells with thicknesses of over 27 μm, this work closes the gap that has existed for much thinner cells. 相似文献
76.
Marcus Schoßig Armin ZankelChristian Bierögel Peter PöltWolfgang Grellmann 《Composites Science and Technology》2011,71(3):257-265
The damage mechanisms of short glass fibre reinforced polypropylene (PP) and polybutene-1 (PB-1) materials were investigated. For this purpose, in situ tensile tests were conducted in the environmental scanning electron microscope (ESEM) while simultaneously recording the acoustic emission (AE). To be able to observe damage mechanisms directly during loading, notched specimens were used. This method allows the direct correlation of the recorded load - elongation data with observed damage mechanisms, as well as correlations with acoustic emission data. Hence, it is possible to describe the damage kinetics of short glass fibre composite.It was found that different bonding conditions of the two investigated materials result in different damage mechanisms as well as in different AE behaviour. For fibre reinforced PP with excellent bonding conditions of the fibres in the polymeric matrix, fibre fracture, slipping of fibres in the delamination area, debonding and pull-out with matrix yielding was observed. The determined AE parameter amplitude Ap and energy EAE for the PB-1 material are lower because of the weak bonding of the fibres to the PB-1-matrix. Hence, energy dissipative damage mechanisms like pull-out with matrix yielding can occur only in a limited part of such materials. 相似文献
77.
Synthesis of novel tricalcium phosphate-bioactive glass composite and functionalization with rhBMP-2
Schickle K Zurlinden K Bergmann C Lindner M Kirsten A Laub M Telle R Jennissen H Fischer H 《Journal of materials science. Materials in medicine》2011,22(4):763-771
A functionalization is required for calcium phosphate-based bone substitute materials to achieve an entire bone remodeling.
In this study it was hypothesized that a tailored composite of tricalcium phosphate and a bioactive glass can be loaded sufficiently
with rhBMP-2 for functionalization. A composite of 40 wt% tricalcium phosphate and 60 wt% bioactive glass resulted in two
crystalline phases, wollastonite and rhenanite after sintering. SEM analysis of the composite’s surface revealed a spongious
bone-like morphology after treatment with different acids. RhBMP-2 was immobilized non-covalently by treating with chrome
sulfuric acid (CSA) and 3-aminopropyltriethoxysilane (APS) and covalently by treating with CSA/APS, and additionally with
1,1′-carbonyldiimidazole. It was proved that samples containing non-covalently immobilized rhBMP-2 on the surface exhibit
significant biological activity in contrast to the samples with covalently bound protein on the surface. We conclude that
a tailored composite of tricalcium phosphate and bioactive glass can be loaded sufficiently with BMP-2. 相似文献
78.
Armin Eftekhari Massoud Babaie-ZadehHamid Abrishami Moghaddam 《Signal processing》2011,91(7):1589-1603
As an alternative to adaptive nonlinear schemes for dimensionality reduction, linear random projection has recently proved to be a reliable means for high-dimensional data processing. Widespread application of conventional random projection in the context of image analysis is, however, mainly impeded by excessive computational and memory requirements. In this paper, a two-dimensional random projection scheme is considered as a remedy to this problem, and the associated key notion of concentration of measure is closely studied. It is then applied in the contexts of image classification and sparse image reconstruction. Finally, theoretical results are validated within a comprehensive set of experiments with synthetic and real images. 相似文献
79.
Maljusch A Schönberger B Lindner A Stratmann M Rohwerder M Schuhmann W 《Analytical chemistry》2011,83(15):6114-6120
The integration of a scanning Kelvin probe (SKP) and a scanning electrochemical microscope (SECM) into a single SKP-SECM setup, the concept of the proposed system, its technical realization, and first applications are presented and discussed in detail. A preloaded piezo actuator placed in a grounded stainless steel case was used as the driving mechanism for oscillation of a Pt disk electrode as conventionally used in SECM when the system was operated in the SKP mode. Thus, the same tip is recording the contact potential difference (CPD) during SKP scanning and is used as a working electrode for SECM imaging in the redox-competition mode (RC-SECM). The detection of the local CPD is established by amplification of the displacement current at an ultralow noise operational amplifier and its compensation by application of a variable backing potential (V(b)) in the external circuit. The control of the tip-to-sample distance is performed by applying an additional alternating voltage with a much lower frequency than the oscillation frequency of the Kelvin probe. The main advantage of the SKP-SECM system is that it allows constant distance measurements of the CPD in air under ambient conditions and in the redox-competition mode of the SECM in the electrolyte of choice over the same sample area without replacement of the sample or exchange of the working electrode. The performance of the system was evaluated using a test sample made by sputtering thin Pt and W films on an oxidized silicon wafer. The obtained values of the CPD correlate well with known data, and the electrochemical activity for oxygen reduction is as expected higher over Pt than W. 相似文献
80.
Melanie Kaiser Maria Donatella Semeraro Markus Herrmann Gudrun Absenger Armin Gerger Wilfried Renner 《International journal of molecular sciences》2021,22(13)
Immune functions decline as we age, while the incidence of cancer rises. The advent of immune checkpoint blockade (ICB) has not only revolutionized cancer therapy, but also spawned great interest in identifying predictive biomarkers, since only one third of patients show treatment response. The aging process extensively affects the adaptive immune system and thus T cells, which are the main target of ICB. In this review, we address age-related changes regarding the adaptive immune system with a focus on T cells and their implication on carcinogenesis and ICB. Differences between senescence, exhaustion, and anergy are defined and current knowledge, treatment strategies, and studies exploring T cell aging as a biomarker for ICB are discussed. Finally, novel approaches to improve immunotherapies and to identify biomarkers of response to ICB are presented and their potential is assessed in a comparative analysis. 相似文献