排序方式: 共有35条查询结果,搜索用时 46 毫秒
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The control of the grain size distribution of the LiCoPO4 compound was achieved by a thermodynamically monitored heating regime of the used ceramic route. For this purpose, on the basis of calorimetric (DSC-TG) measurements collected in non-isothermal and isothermal regime and then related to the grain size of the final product via equations, the irreversibility degree of the heating regime was determined. Grain size of the final product was revealed by scanning electron microscopy (SEM), while the purity of the final product was discussed from thermodynamic calculations (DSC and TG) and confirmed by X-ray diffraction analysis (XRD). The purity and the grain size of the product was tested a priori, using a series of heating regimes and then the accuracy of the established model was checked. 相似文献
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We demonstrate full characterization of femtosecond pulse distortion induced by all-order polarization mode dispersion (PMD) at selected polarization states via second-harmonic generation (SHG) frequency-resolved optical gating (FROG) measurements at an average power of under 28 nW. By applying the inverse of the measured spectral phase via a programmable pulse shaper, we compress the distorted pulses from more than 3 ps to nearly bandwidth-limited durations of less than 500 fs. Our results show that SHG FROG measurements performed by using fiber-pigtailed aperiodically poled lithium niobate waveguides can serve as a robust and sensitive tool for characterization of PMD-induced spectral phase. 相似文献
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Described herein are two series (twelve compounds each) of very closely related guanidinium‐based receptors and their ability to catalyze hydrolytic cleavage of a unique RNA substrate – oligo‐dT flanked t rans‐ A ctivation R esponsive region of the HIV‐1 mRNA, TAR RNA. The significant difference in activities of otherwise very similar compounds is discussed, and direct and indirect evidences supporting our interpretation are presented. The results indicate that improvements in catalytic efficiency could be achieved with little modification of the structure of a relatively weak catalyst, and that a crucial feature could be a finely calibrated interplay between anion‐binding and proton‐donating abilities. 相似文献
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N. Minkov S. B. Drenska P. P. Raychev R. P. Roussev D. Bonatsos 《Physics of Atomic Nuclei》2001,64(6):1098-1104
We propose a collective Hamiltonian that incorporates interactions capable of generating rotations in nuclei with simultaneous presence of octupole and quadrupole deformations. It is demonstrated that the model formalism could be applied to reproduce the staggering effects observed in nuclear octupole bands. On this basis, we propose that the interactions involved would provide a relevant handle in the study of collective phenomena in nuclei and other quantum mechanical systems with reflection asymmetry correlations. 相似文献
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We propose several techniques to modulate the local amplitude of quasi-phase-matched (QPM) interactions in periodically poled lithium niobate waveguides and demonstrate apodization by using each of these techniques. When the hard edges are removed in the spatial profile of the nonlinear coupling, the sidelobes of the frequency tuning curves are suppressed by 13 dB or more, compared with a uniform grating, consistent with theoretical predictions. The sidelobe-suppressed gratings are useful for frequency conversion devices in optical communication systems to minimize interchannel cross talk, while the amplitude modulation techniques in general have potential uses in applications that require altering the tuning curve shapes. 相似文献
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Chui HC Shaw SY Ko MS Liu YW Shy JT Lin T Cheng WY Roussev RV Fejer MM 《Optics letters》2005,30(6):646-648
The iodine molecule has frequently been used as a frequency reference from the green to the near-infrared wavelength region (500-900 nm). We describe the frequency locking of the second-harmonic signal of a 197.2-THz (1520.25-nm) distributed-feedback diode laser to the absorption lines of the iodine hyperfine structure; a frequency jitter below 0.1 MHz was achieved at a 300-ms time constant. This scheme provides a simple, compact, and high-performance frequency reference in the optical communication band. 相似文献
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K. Blagoev R. Roussev A. Morozov K. Iskra L. Windholz 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(2):159-163
Radiative lifetimes of 7d, 8d 1
D
2 excited states of Hg I are measured using pulsed two-photon excitation from the ground [Xe]5d
106s
2
1
S
0 mercury state, detecting the decay of the laser-induced fluorescence. The results are compared with theoretical values, obtained
by means of a Hartree-Fock single configuration method, taking into account electron configuration interaction. The radiative
lifetime value dependence on the effective principal quantum number for the nd 1
D
2 series is analyzed and compared with the quantum defect dependence.
Received 25 February 2000 and Received in final form 26 July 2000 相似文献