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1.
The Bloch mode propagation through the chirped periodical structure is defined by its local dispersion relation. In a slowly varying structure its time delay is the integral of the local inverse group velocity along the propagation direction. The integration can be strongly simplified for linearly chirped structures if the assumption is made that the local dispersion relation is just a scaled and shifted version of the dispersion relation at the input. This assumption leads to exact solutions for the structures with locally uniaxial deformation and provides a good approximation for arbitrary structures with small chirps. The approach is demonstrated for high index contrast chirped Bragg mirrors and complicated photonic crystal waveguide structures, including coupled waveguides and a slow group velocity waveguide. 相似文献
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Chloride‐induced damage of reinforcing steel is especially for parking garages and bridges often very severe as large amounts of chlorides act on horizontal surfaces which could lead to fast ingress of these detrimental ions up to the level of the reinforcement and subsequently to high rates of corrosion. In order to avoid the disadvantages of conventional rehabilitation (unreliable prognosis with patch repair or high costs and regular maintenance with cathodic protection using impressed current) a new combined protection system was developed where the principle of drying out the concrete (by means of a surface protection system) is combined with a temporary cathodic protection (by means of a sprayed zinc layer) during the transitional period of the drying out process. This new system was tested both in the laboratory and on‐site at a pilot application. Based on the results obtained the possibilities and limitations of the new system are discussed in this paper. 相似文献
6.
G. Eich J. von Czarnecki C. Eisenschink 《Journal of Failure Analysis and Prevention》2011,11(6):661-665
Several electrical brass (CuZn37) connector bolts of aircraft batteries failed as a result of stress-corrosion cracking. The
batteries are used for emergency supply of the avionics in case of power failure or for complete control in the case of engine
failure. For activation, the thermal battery is heated by a pyrotechnic element and then supplies electrical power with 5 A
for 20 min up to 240 A for 3 min. For assembly of the batteries, an acetic acid curing silicone resin is used for housing
seal on the lid and on the connector bolts. Because of the almost hermetic sealing of the enclosure, the silicone resin cures
very slowly and metallic parts are exposed to the acetic acid vapor. So the electrical brass connector showed corrosive attack
with the formation of copper acetate (verdigris). Subsequent failure due to stress-corrosion cracking occurred. The failure
type and damage mechanisms could be simulated in laboratory experiments. 相似文献
7.
G. Eich 《Journal of Failure Analysis and Prevention》2012,12(5):490-493
Incorrect material selection does not always lead to corrosion. In addition to an inferior selection of materials, unsuitable operating conditions and poor design also contributed to the presented failure. A combination of erosion and corrosion caused a leak in an oil cooler of a Navy ship. Because there was no welding seam between the deflectors and tube plate on the carbon steel cooler, cooling water could stream between them, and the flow rate became excessive. This caused erosion on the tube plate. In addition, the repeated change of the cooling liquid after servicing caused a uniform corrosion attack. 相似文献
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Converging evidence from 3 studies suggests that how well information transfers from one environment to another depends on how similar the environments feel rather than on how similar they look. Thus, even when target events are encoded and retrieved in the same physical setting, memory performance suffers if the attending affective states differ. Conversely, a change in environment produces no performance decrement if, whether by chance (Experiments 1 and 2) or by design (Experiment 3), the mood at encoding matches the mood at retrieval. These observations imply that place dependent effects are mediated by alterations in affect or mood, and that data that appear on the surface to demonstrate place dependent memory may, at a deeper level, denote the presence of mood dependent memory. Discussion focuses on prospects for future research aimed at clarifying the relations among moods, places, and memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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M. Walther R. Rehm F. Fuchs J. Schmitz J. Fleißner W. Cabanski D. Eich M. Finck W. Rode J. Wendler R. Wollrab J. Ziegler 《Journal of Electronic Materials》2005,34(6):722-725
An infrared camera based on a 256×256 focal plane array (FPA) for the second atmospheric window (3–5 μm) has been realized
for the first time with InAs/GaSb short period superlattices (SLs). The SL detector structure with a broken gap type-II band
alignment was grown by molecular beam epitaxy on GaSb substrates. Effective bandgap and strain in the superlattice were adjusted
by varying the thickness of the InAs and GaSb layers and the controlled formation of InSb-like bonds at the interfaces. The
FPAs were processed in a full wafer process using optical lithography, chemical-assisted ion beam etching, and conventional
metallization technology. The FPAs were flip-chip bonded using indium solder bumps with a read-out integrated circuit and
mounted into an integrated detector cooler assembly. The FPAs with a cut-off wavelength of 5.4 μm exhibit quantum efficiencies
of 30% and detectivity values exceeding 1013 Jones at T=77 K. A noise equivalent temperature difference (NETD) of 11.1 mK was measured for an integration time of 5 ms
using f/2 optics. The NETD scales inversely proportional to the square root of the integration time between 5 ms and 1 ms,
revealing background limited performance. Excellent thermal images with low NETD values and a very good modulation transfer
function demonstrate the high potential of this material system for the fabrication of future thermal imaging systems. 相似文献
10.
A monolithic waveguide system using poly(dimethyl siloxane) (PDMS) was designed, fabricated, and characterized. The waveguide demonstrated good confinement of light and relatively low attenuation at 0.40 dB/cm. The robustness and handling properties of the completed waveguides were excellent, and the process yield exceeded 96%. The waveguide did exhibit moderate temperature and humidity sensitivity but no temporal variation, and insertion loss remained stable over extended periods of time. Applications of this waveguide system in microscale sensing are immense, judging by the frequency of use of PDMS as the substrate for microfluidic and biomedical systems. The monolithic nature of the waveguides also reduces their cost and allows integration of optical pathways into existing PDMS-based microsystems. 相似文献