排序方式: 共有30条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Fuel cells for homes and hospitals 总被引:2,自引:0,他引:2
Along with promising car and bus applications, fuel cells in stationary versions are being designed to power single homes and large buildings. Some systems gain more output power by operating the cell in combination with a gas turbine. The author discusses the basic principles of fuel cells and fuel processing technology. Fuel cells for residential applications and combined gas turbine/fuel cell systems are also discussed. The key to increased use of fuel cells is cost reduction at the production stage 相似文献
5.
Barrier height engineering of n-GaAs-based millimeter-wave Schottky diodes using strained InGaAs/GaAs and InGaP/GaAs heterostructures and a high doping surface layer is presented. The Schottky barrier height can be varied between Φfb=0.52 eV and Φfb=1.0 eV. The use of a pseudomorphic InGaAs layer and/or a thin high doping layer at the surface significantly reduces the Schottky barrier height. This is advantageous for low-drive zero bias mixing applications, A full quantum mechanical numerical calculation is presented to simulate the influence of different high doping layer thicknesses on the diode's dc characteristic. The theoretical results are compared with experimental results, For reverse bias applications (e.g., varactors) a barrier height and breakdown voltage enhancement is realized with a lattice matched InGaP/GaAs heterostructure. The barrier height value is determined by temperature dependent dc-measurements. The epitaxial layered structures are grown by molecular beam epitaxy. The diode devices are fabricated in a fully planar technology using selective oxygen implantation for lateral isolation. The diode's cut-off frequencies are in the THz-range 相似文献
6.
GaAs based HEMT devices were fabricated with a constant recess towards the source, whereas the recess width towards the drain was varied. While the off-state breakdown voltage has been improved by the use of a wide recess towards the drain, no dependence of the on-state breakdown on the recess configuration was observed. The constant breakdown voltage in the on-state is analysed by the feedback parameters obtained from an extraction of the small signal equivalent circuit. Although the extrinsic gate drain capacitance could be reduced by the use of a wider recess configuration, it is assumed that the intrinsic drift region is independent of the recess configuration 相似文献
7.
8.
We consider a variety of commutative operator semigroups, that is, of algebras with a unary operation and a binary commutative
and associative operation. Asubpartition of a set is a partition of a subset of the set. For each integern>0, we represent the subpartitions on ann-element set asn-ary terms in the variety. We determine necessary and sufficient conditions on the variety ensuring that there be no constant
terms and, for eachn>0, that these representing terms be all the essentiallyn-ary terms and moreover that distinct subpartitions yield distinct terms. We show that there is precisely one such variety
of commutative operator semigroups. 相似文献
9.
10.
Kamrath MZ Garand E Jordan PA Leavitt CM Wolk AB Van Stipdonk MJ Miller SJ Johnson MA 《Journal of the American Chemical Society》2011,133(16):6440-6448
We present infrared photodissociation spectra of two protonated peptides that are cooled in a ~10 K quadrupole ion trap and "tagged" with weakly bound H(2) molecules. Spectra are recorded over the range of 600-4300 cm(-1) using a table-top laser source, and are shown to result from one-photon absorption events. This arrangement is demonstrated to recover sharp (Δν ~6 cm(-1)) transitions throughout the fingerprint region, despite the very high density of vibrational states in this energy range. The fundamentals associated with all of the signature N-H and C=O stretching bands are completely resolved. To address the site-specificity of the C=O stretches near 1800 cm(-1), we incorporated one (13)C into the tripeptide. The labeling affects only one line in the complex spectrum, indicating that each C=O oscillator contributes a single distinct band, effectively "reporting" its local chemical environment. For both peptides, analysis of the resulting band patterns indicates that only one isomeric form is generated upon cooling the ions initially at room temperature into the H(2) tagging regime. 相似文献