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Rajind Mendis Cezary Sydlo Jochen Sigmund Michael Feiginov Peter Meissner Hans L. Hartnagel 《International Journal of Infrared and Millimeter Waves》2005,26(2):201-207
We report on a completely coherent, tunable, continuous-wave THz system where, for the first-time, both the transmitter and receiver are log-periodic-antenna coupled LTG-GaAs based finger-photomixers. This compact room-temperature system exhibits signal-to-noise ratios (> 103) comparable to or better than what is reported in the literature, and has potential applications in high-resolution spectroscopy and imaging. For the purpose of demonstration, we also present results of spectroscopy measurements carried out on fused silica, which are in agreement with previously published THz-TDS measurements. 相似文献
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Halochromic Molecules. Synthesis and Acidobasic Properties of Substituted Heteroarenoquinazolines We have synthetized a series of substituted heteroarenoquinazolines. The 90-MHz FT 1H-NMR spectra of starting and final products supported the postulated structures. Fragmentation in the mass spectra also were consistant with the assumed structures. With acid, the compounds partly from ring-opened, intensely coloured triphenylcarbenium salts of the Rhoduline-R type (C. I. 42565). UV/VIS spectra of the salts are discussed on the basis of VEPPP-CI calculations. The ?pH* curves in buffered MeOH/H2O solutions and the pK* values are determined. The title compounds undergo very complex protonation equilibria. 相似文献
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Karl Sigmund 《Annals of Operations Research》1992,37(1):217-228
In many cases, the orbits of deterministic systems displaying highly irregular oscillations yield smoothly converging time averages. It may happen, however, that these time averages do not converge and themselves display wild oscillations. This is analyzed for heteroclinic attractors and hyperbolic strange attractors. 相似文献
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Using the Generalized Master Equation (GME) we investigate the dynamics of a two-level system which is subjected both to the influence of a thermal reservoir and to an external driving field. The coupling with the phonon reservoir is represented by the usual (energy-conserving) linear-displacements interaction, which makes the model exactly solvable in the absence of the external field. The coupling with the external field is treated within the Rotating Wave Approximation (RWA). We obtain an exact formal solution of the GME and we construct a hierarchical class of weak-driving approximations avoiding usual assumption of a weak coupling to the bath. The populational difference is damped in a nontrivial manner: the relaxation is nonexponential with long-time tail behaviour in the asymptotic region. The evolution is analysed as a function of temperature, the strength of the coupling, the strength of the external field and the detuning. Our model is formally identical to the spin-boson model and our approach gives a systematic improvement of the noninteracting-blip approximation. 相似文献
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