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排序方式: 共有1100条查询结果,搜索用时 46 毫秒
51.
52.
Electrical contact resistance between stainless steel bipolar plate and carbon felt in PEFC: A comprehensive study 总被引:1,自引:0,他引:1
Johan André Laurent Antoni Jean-Pierre Petit Eric De Vito Alexandre Montani 《International Journal of Hydrogen Energy》2009
Bipolar plate represents a key component of Proton Exchange Membrane Fuel Cell (PEFC) with several essential functions, among them the electric connection of elementary cells. Usually made of graphite, this component is studied worldwide in order to develop a commercially viable alternative: different ways have been being investigated, and to date, despite corrosion issues, stainless steel (SS) appears as a good candidate material, but its Electrical Contact Resistance (ECR) can reach unacceptable values when exposed to PEFC environment. This paper offers a comprehensive study of the parameters acting on ECR when using uncoated SS in PEFC: roughness, which influences the surface contact area with carbon baking, bulk composition of the alloy, which influences only partly the nature of passive films, and the composition and structure of passive films, strongly modified by surface treatments and ageing conditions. 相似文献
53.
54.
Michael G. Debije Jean-Pierre Teunissen Paul P.C. Verbunt 《Solar Energy Materials & Solar Cells》2009,93(8):1345-1350
The effect of adding white scattering layers to the bottom side of luminescent solar concentrator waveguides is evaluated. It is determined that adding a rear scatterer separated from the waveguide by an air gap results in a large increase of energy output from the waveguides, and this enhancement persists over long (>30 cm) distances, although the magnitude of the enhancement decreases with distance. An attached scatterer resulted in the greatest improvement of light output for short (∼6 cm) distances, but actually reduced edge emissions over longer distances. We provide estimates for the relative contribution of dye-emitted light and scattered light to the total waveguide emission, as well as distinguishing between the contributions of direct and indirect scattering of light to the total output as a function of dye content of the waveguides. 相似文献
55.
The textural characteristics of three commercial activated carbons, Filtrasorb 400 (F400), Industrial React High Affinity
and Picabiol, commonly used in water treatment, are reinvestigated. Nitrogen physisorption isotherms are determined in the
range P/P
0 = [4 × 10−7–0.998] and processed using BET, αS (Sing), Dubinin–Radushkevich and Density Functional Theory methods. In addition, fractal dimensions are determined by the
Frenkel–Halsey–Hill procedure. Since F400 is often considered as a reference material in studies on the adsorption of solutes
in aqueous solutions, a review of the textural characteristics of this carbon is carried out. The results obtained in this
work using the different methods are consistent and a critical crossed comparison of these results allows discussing the limitations
of the methods used. In particular, the impact of the P/P
0 range considered on S
BET value is examined. In addition, the accuracy of the BET specific surface area is assessed in the light of information from
recent literature. 相似文献
56.
This paper deals with a well-known problem in the general area of search theory: optimize the search resources sharing so as to maximize the probability of detection of a (moving) target. However, the problem we consider here considerably differs from the classical one. First, there is a bilevel search planning and we have to consider jointly discrete and continuous optimization problems. To this perspective original methods are proposed within a common framework. Furthermore, this framework is sufficiently general and versatile so as to be easily and successfully extended to the difficult problem of the multizone multisensor search planning for a Markovian target. 相似文献
57.
Magalie Laniel Jean-Pierre Emond Ahmet E. Altunbas 《Sensing and Instrumentation for Food Quality and Safety》2009,3(1):34-40
The performance of radio waves in open environments has been studied for years. In contrast, the behavior of Radio Frequency
Identification (RFID) inside metal enclosed areas is not yet understood. This research project focuses on the 3-D mapping
of RFID signal strength inside a 12 m refrigerated marine container instrumented with three different types of radio frequency
(RF) emitters: 915 MHz reader; 2.45 GHz reader and 433 MHz RF transmitter. The main goal is to find a frequency/configuration
that would allow real time reading of the temperature in a shipment of perishable products using RFID. Only one frequency
and one antenna were used at a time. The RF transmitter antenna was mounted at two different places inside the container;
at the top of the front wall (facing back) and on the ceiling in the middle of the container (facing down). The signal strength
was acquired by a spectrum analyzer and its antenna was mounted on a small electric cart inside the container. The cart was
programmed to move along the length of the container and stop repeatedly, allowing three automated measures per position.
All data were analyzed in terms of power level and attenuation. The maps showed that the RFID antenna positioned at the front
of the container delivered slightly better results than the one in the middle of the ceiling. The results showed a significantly
higher performance at the 433 MHz level.
This article was presented at Food Processing Automation Conference, American Society of Agricultural and Biological Engineering
(ASABE), Providence, RI, June 28–29 2008. 相似文献
58.
The in situ tensile straining of cross-sectional specimens inside a TEM is intrinsically very difficult to perform despite its obvious interest to study interfaces of surface treated materials. We have combined a FIB-based method to produce H-bar specimens of a nitrided Ti-6Al-4V alloy and in situ TEM straining stage, to successfully study the plastic deformation mechanisms that are activated close to the nitrided surface in the Ti-based alloy. 相似文献
59.
Jean-Pierre Bibring 《e & i Elektrotechnik und Informationstechnik》2002,119(9):a17-a17
SciencenewsTu Wien
Software für den Mars 相似文献60.
Morvan L Lai ND Dolfi D Huignard JP Brunel M Bretenaker F Le Floch A 《Applied optics》2002,41(27):5702-5712
A new principle of lidar-radar is theoretically and experimentally investigated. The proposed architecture is based on the use of an rf modulation of the emitted light beam and a direct detection of the backscattered intensity. Use of a radar-processing chain allows one to obtain range and Doppler measurements with the advantages of lidar spatial resolution. We calculate the maximum range of this device, taking into account different possible improvements. In particular, we show that use of a pulsed two-frequency laser and a spatially multimode optical preamplification of the backscattered light leads to calculated ranges larger than 20 km, including the possibility of both range and Doppler measurements. The building blocks of this lidar-radar are tested experimentally: The radar processing of an rf-modulated backscattered cw laser beam is demonstrated at 532 nm, illustrating the Doppler and identification capabilities of the system. In addition, signal-to-noise ratio improvement by optical pre-amplification is demonstrated at 1.06 microm. Finally, a two-frequency passively Q-switched Nd:YAG laser is developed. This laser then permits two-frequency pulses with tunable pulse duration (from 18 to 240 ns) and beat frequency (from 0 to 2.65 GHz) to be obtained. 相似文献