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301.
Muhammad A. Rashid Bettina Appel Vahuni Karapetyan Helmut Reinke Peter Langer 《Tetrahedron》2008,64(22):5416-5425
Functionalized 1-azaxanthones (5-oxo-5H-[1]-benzopyrano[2,3-b]pyridines) were prepared by TMSOTf-mediated condensation of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with 3-cyanochromones and subsequent base-mediated domino ‘retro-Michael/nitrile-addition/heterocyclization’ reaction. 相似文献
302.
A.A. Puretzky D.B. Geohegan S. Jesse I.N. Ivanov G. Eres 《Applied Physics A: Materials Science & Processing》2005,81(2):223-240
Direct measurements of carbon nanotube growth kinetics are described based upon time-resolved reflectivity (TRR) of a HeNe laser beam from vertically aligned nanotube arrays (VANTAs) as they grow during chemical vapor deposition (CVD). Growth rates and terminal lengths were measured in situ for VANTAs growing during CVD between 535 °C and 900 °C on Si substrates with evaporated Al/Fe/Mo multi-layered catalysts and acetylene feedstock at different feedstock partial pressures. Methods of analysis of the TRR signals are presented to interpret catalyst particle formation and oxidation, as well as the porosity of the VANTAs. A rate-equation model is developed to describe the measured kinetics in terms of activation energies and rate constants for surface carbon formation and diffusion on the catalyst nanoparticle, nanotube growth, and catalyst over-coating. Taken together with the TRR data, this model enables basic understanding and optimization of growth conditions for any catalyst/feedstock combination. The model lends insight into the main processes responsible for the growth of VANTAs, the measured number of walls in the nanotubes at different temperatures, conditions for growth of single-wall carbon nanotube arrays, and likely catalyst poisoning mechanisms responsible for the sharp decline in growth rates observed at high temperatures. PACS 61.46.+w; 81.07.De; 81.16.Hc 相似文献
303.
L. Appel A. Al-Khayat B. Babol R. Bolzer L. Faltin G. Humer M. Lenger W. Maluenda M. Meyenburg R. Scherzer G. Steinböck 《e & i Elektrotechnik und Informationstechnik》2002,119(2):44-47
As part of a joint research project a hardware real time simulator for smart antennas was developed. The simulator allows for the simulation and evaluation of smart antenua algorithms. Simulations are carried out in the baseband domain and consist of a transmitter (GSM signal generator), mobile transmission channels for multiple receiveing antennas (Geometry-based Stochastic Channel Model according to COST259), (GSM-) co-channel interferers, and a multi-channel mobile terminal receiver using smart antenna algorithms. Typical results are presented. 相似文献
304.
Zheng J 《Optics letters》2005,30(1):17-19
An all-fiber single-mode fiber unbalanced Sagnac gyroscope is described. The gyroscope is based on optical frequency-modulated continuous-wave interference and consists primarily of four Y-type single-mode fiber directional couplers and a single-mode fiber coil. The rotational velocity of the fiber coil is determined simultaneously by detection of the phase shift of the beat signal. The advantages and limitations of the gyroscope are discussed. 相似文献
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