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排序方式: 共有159条查询结果,搜索用时 15 毫秒
1.
Lott J.A. Schneider R.P. Jr Vawter G.A. Zolper J.C. Malloy K.J. 《Electronics letters》1993,29(4):328-329
The demonstration of the first visible resonant cavity light-emitting diodes (RCLEDs) is reported. The devices consist of an InAlGaP strained quantum well active region surrounded by AlAs/AlGaAs distributed Bragg reflectors. Linewidths from 0.9 mm (2.6 meV) to 45 nm (12.8 meV) were obtained by varying the cavity factor (Q).<> 相似文献
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Piasecki E Bresson S Lott B Bougault R Colin J Crema E Galin J Gatty B Genoux-Lubain A Guerreau D Horn D Jacquet D Jahnke U Jastrzebski J Kordyasz A Le Brun C Lecolley JF Louvel M Morjean M Paulot C Pienkowski L Pouthas J Quednau B Schröder WU Schwinn E Skulski W Töke J 《Physical review letters》1991,66(10):1291-1294
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Hunsucker R.D. Coker C. Cook J. Lott G. 《Antennas and Propagation, IEEE Transactions on》1995,43(11):1313-1318
VHF propagation on ⩽5300 km polar paths has been documented during the maximum phase of sunspot cycle 19. Mode analysis on these polar paths has shown that auroral-E ionization (AEI) supported some modes. Electron densities and plasma frequencies which could support AEI modes at frequencies up to 46 MHz have also been measured. Long distance VHF propagation from AEI has also been reported by radio amateurs using frequencies in the 2 m band in a “sidescatter mode”. An AEI experiment has been in operation between Wales (Alaska) and Fairbanks (Alaska) where a 75-watt CW transmitter located in Wales transmits the Morse letter “R” every 5 s, and a receiver in Fairbanks detects the 25.5 MHz signal whenever AEI is present near the midpoint of the 960 km path. Another experiment is underway using a GPS total electron content (TEC) receiving station at Fairbanks also using AEI data from the Wales-Fairbanks experiment. From this, the authors examine 58 passes of GPS satellites whose E-layer penetration points lie close to the midpoint of the Wales-Fairbanks path and find that there is a threshold value of TEC above which auroral-E (AE) propagation occurs. They also find that AEI propagation is strongly correlated with large- and medium-scale E-region structures in TEC determined by the GPS measurements. When TEC ionospheric structures are not present near the Wales-Fairbanks path midpoint, no AEI signal is received. The authors tentatively conclude that the occurrence of these specific TEC signatures may be utilized as predictors of AEI forward propagation on paths within and parallel to the auroral oval 相似文献
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A method has been developed for the fluorimetric determination of selenium in plant material using the reagent 2,3-diaminonaphthalene. Oxygen-flask combustion is used to oxidize plant material. Isotopic dilution techniques are incorporated to account for loss in different stages of the procedure. Measurements are also included on the suitability of several other amines as reagents for selenium. 相似文献
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John Lott 《Journal of Geometric Analysis》2000,10(3):529-543
If M is a compact spin manifold, we give relationships between the vanishing of Â(M) and the possibility that M can collapse with curvature bounded below. 相似文献
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Presents a semi-analytic full-vector method for calculating the spatial profile, optical confinement factor resonant frequency, absorption loss, and mirror loss of lasing modes in cylindrically symmetric microcavity vertical-cavity surface-emitting lasers (VCSEL's). It can be shown that this method gives the best separable approximation for the electric and magnetic vector potentials. Our technique can model the entire VCSEL structure and can treat complex media. We apply the method to etched-post and oxide-apertured VCSEL's designed for 980-nm emission and find a blueshift in cavity resonance as the cavity radius shrinks. We also find a minimum optical cavity radius below which radially bound lasing modes cannot be supported. This radius depends on the device geometry and lies between 0.5 and 1 μm for the devices studied. Once this model is augmented to include diffraction losses-the dominant loss mechanism for conventional small aperture lasers-it will provide a complete picture of lasing eigenmodes in microcavity VCSEL's 相似文献