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991.
992.
The interactions induced by the nonlinear refractive index in a single-mode optical fiber (Kerr effect) between a modulated wave and a carrier wave have been investigated for amplitude shift keying (ASK), frequency shift keying (FSK), and phase shift keying (PSK). The theoretical analysis, based on a time-domain solution, exploits the well-known formalism of self-phase modulation to describe the propagation of the input electric field in the fiber. The theoretical results were validated experimentally for amplitude- and phase-modulated waves with heterodyne detection techniques. These experiments mimic a coherent transmission system and allow the measurement of the spectrum of each of the waves that participate in the nonlinear interaction 相似文献
993.
Streit D.C. Oki A.K. Umemoto D.K. Velebir J.R. Stolt K.S. Yamada F.M. Saito Y. Hafizi M.E. Bui S. Tran L.T. 《Electron Device Letters, IEEE》1991,12(9):471-473
The authors have developed a modified MBE growth process to produce high-gain n-p-n GaAs-AlGaAs heterojunction bipolar transistors (HBTs) with a mean time to failure (MTTF) of 1.5×108 h at 125°C. Beryllium incorporation and diffusion are controlled through a combination of reduced substrate temperature and increased As/Ga flux ratio during MBE growth, resulting in extremely stable HBT profiles. The authors also demonstrate graded InGaAs surface layers with nonalloyed refractory metal contacts that significantly improve ohmic reliability compared to alloyed AuGe contacts. The ability to produce robust HBTs by MBE is critically important to this technology 相似文献
994.
A. F. Carley 《Catalysis Today》1992,12(4):413-419
During the past 15 years the advent of laboratory microcomputers has had a dramatic effect on the information we can extract from spectroscopic data. In this paper we take a brief look at the historical development of this field, consider some of the techniques being currently researched, and comment on possible future trends. 相似文献
995.
A number of copolymers were synthesised by condensing the 2,4-dinitrophenylhydrazone of resacetophenone with substituted benzoic acids/ phenols and formaldehyde in the presence of sodium hydroxide or hydrochloric acid. The decomposition temperature, solubility and viscosity of the polymers have been determined. The ion-exchange properties have been studied by using a batch equilibrium method. The distribution of a number of metal ions between an aqueous solution and the resin have been measured. A wide range of pH and variable ionic strengths have been investigated. 相似文献
996.
The large amplitude oscillatory shear test has been used to discriminate subtle differences in nonlinear viscoelasticity between two high density polyethyene blow molding resins with different processability. Structural network theory was used to explain the subtle differences in terms of entanglement kinetics with remarkable accuracy. The resin with better shape retention characteristics in programmed parison blow molding was found to have a higher kinetic rate constant for molecular re-entanglement. 相似文献
997.
Marti J. Pastor D. Tortola M. Capmany J. Montero A. 《Lightwave Technology, Journal of》1997,15(2):179-187
We report on the use of tapered linearly chirped fiber gratings to equalize dispersion-induced distortion in long distance/broad-band subcarrier multiplexed (SCM) systems. Different apodization functions for the coupling factor of the fiber grating have been considered and their equalizing capability of fiber-induced distortion in a subcarrier system have been compared. The results of the theoretical analysis show that both harmonic and intermodulation distortions are significantly reduced when the equalizer parameters have been properly designed. Higher reduction of the nonlinear distortion is obtained when the length of the filter increases, even though a saturation effect on this reduction figure appears when the equalizer length is about four or five times its minimum value to achieve equalization, which is derived theoretically based on the SCM optical system parameters. The performance of a Tanh-type tapered linearly chirped grating equalizer on a realistic broadband SCM system is also considered. The results reveal that the dispersion-induced distortion can be neglected when the equalizer is employed 相似文献
998.
Translated from Fiziko-Khimicheskaya Mekhanika Materialov, No. 5, pp. 51–56, September–October, 1992. 相似文献
999.
1000.