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861.
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865.
Liying Tan Qingbo Yang Jing Ma Siyuan Yu Qiqi Han Yijun Jiang 《Journal of Russian Laser Research》2011,32(3):209-215
We analyze the performance of a satellite-to-ground downlink coherent lasercom system taking into account the combined effects
of atmospheric wavefront aberration and tracking error of the receiver. We revise the wavefront phase variance in the case
where the tracking error of the receiver terminal is present. We consider the example of the BPSK modulation scheme and show
that the tracking error of the receiver terminal greatly increases the bit error probability of the coherent system. We show
the optimum aperture diameter of the receiver. This study can benefit the satellite-to-ground downlink coherent lasercom system
design. 相似文献
866.
Jamie YuLing Han Timothy Thatt Yang Tan Joachim Say Chye Loo 《Journal of nanoparticle research》2011,13(8):3441-3454
The aim of this study was to investigate the feasibility of the inverse micelles (IM) technique in producing protein-loaded
calcium phosphate nanoparticles (CaP NPs), and to compare this technique with the conventional co-precipitation (co-ppt) technique.
In this study, bovine serum albumin and lysozyme were used as model proteins. The results show that CaP NPs produced by IM
were shown to be spherical and homogenous in size of ~50 nm. Protein loading efficiency of the IM technique was shown to be
much higher than CaP NPs synthesized through co-ppt technique. X-ray photoelectron spectroscopy shows that proteins were not adsorbed onto the surface of IM-synthesized CaP NPs, which suggested
that the proteins were entrapped within the particle matrix. Release studies show that protein release was more rapid at lower
pH conditions (pH 5 and 6) than at physiological pH of 7.4. A burst release was observed for co-ppt CaP NPs, while a continuous
release of protein was observed for IM-produced CaP NPs. This study shows the superiority of the IM technique in preparing
pH responsive CaP NPs as nano-carriers. 相似文献
867.
Using the algebraic dynamical method,the entanglement dynamics of an atom-field bipartite system in a mixed state is investigated.The atomic center-of-mass motion and the field-mode structure are also included in this system.We find that the values of the detuning and the average photon number are larger,the amplitude of the entanglement is smaller,but its period does not increase accordingly.Moreover,with the increase of the field-mode structure parameter and the transition photon number,the amplitude of the entanglement varies slightly while the oscillation becomes more and more fast.Interestingly,a damping evolution of the entanglement appears when both the detuning and the atomic motion are considered simultaneously. 相似文献
868.
L. Tan L. W. Liu Y. F. Sun 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,61(1):161-169
A theoretical study is carried out for the cavity
cooling of a Λ-type three-level atom in a high-finesse
optical cavity driven by a weakly field. Analytical expressions
for the friction, diffusion coefficients and the equilibrium
temperature are obtained by using the Heisenberg equations, then
they are calculated numerically and shown graphically as functions
of the controlling parameters. For a suitable choice of these
parameters, the dynamics of the cavity field interaction with the
Λ-type three-level atom introduces a sisyphus cooling
mechanism yielding lower temperature than the one of the two-level
atom, avoiding the problems induced by spontaneous emission. 相似文献
869.
The single-molecule surface-enhanced Raman scattering(SERS) spectra of Rhodamine 6G(R6G) in an aqueous environment under non-resonance conditions are studied.Series of spectra are recorded in timemapping mode,and intensity fluctuations of SERS signals and spectral diffusion are observed.The correlations between the presence frequency of SERS spectra and number of hot spots as well as the quantity of molecules in scattering volume are examined thoroughly.The results indicate that only molecules located at hot spots produce good signal-to-noise ratio Raman spectra and the origin of fluctuating SERS signals are mainly ascribed to the movement of hot spots. 相似文献
870.
Morphology evolution of prior β grains of laser solid forming (LSF) Ti-xAl-yV (x 11,y 20) alloys from blended elemental powders is investigated. The formation mechanism of grain morphology is revealed by incorporating columnar to equiaxed transition (CET) mechanism during solidification. The morphology of prior β grains of LSF Ti-6Al-yV changes from columnar to equiaxed grains with increasing element V content from 4 to 20 wt.-%. This agrees well with CET theoretical prediction. Likewise, the grain morphology of LSF Ti-xAl-2V from blended elemental powders changes from large columnar to small equiaxed with increasing Al content from 2 to 11 wt.-%. The macro-morphologies of LSF Ti-8Al-2V and Ti-11Al-2V from blended elemental powders do not agree with CET predictions. This is caused by the increased disturbance effects of mixing enthalpy with increasing Al content, generated in the alloying process of Ti, Al, and V in the molten pool. 相似文献