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161.
Second harmonic generation of propagating collective excitations in Bose-Einstein condensates
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We consider a possible second harmonic generation (SHG) of propagating collective excitations in a two-component Bose-Einstein condensate (BEC) with repulsive atom-atom interactions. We show that the phase-matching condition for the SHG can be fulfilled if the wave vectors and frequencies of the excitations are chosen adequately from different dispersion branches. We solve the nonlinear amplitude equations for the SHG derived using a method of multiple-scales and provide SHG solutions similar to those obtained for a SHG in nonlinear optical media. A possible experimental realization of the SHG for the propagating collective modes in a cigar-shaped two-component BEC is also discussed. 相似文献
162.
We have studied the densification behaviour, microstructure and electrical properties of WO_3 ceramics with V_2O_5 as the additive ranging from 0.5 to 15mol%. Scanning electron microscopic photos indicated that the grain size of WO_3-V_2O_5 specimens is smaller than that of pure WO_3. The addition of V_2O_5 to WO_3 showed a tendency to enhance the densification rate and to restrict the grain growth. Electrical properties of all specimens were measured for different electrodes at different temperatures. The formation of the grain boundary barrier layer was confirmed by the non-ohmic I-V behaviour. The nonlinear coefficient was obtained at the current density J=0.01, 0.1 and 1mA/cm^2 for a series of WO_3-V_2O_5 samples. The V0.5mol% specimen showed an abnormal phenomenon that the nonlinear characteristics appeared at 350℃ and disappeared at lower and higher temperatures. This implies that it could be applied as a high-temperature varistor. The double Schottky barrier model was adopted to explain the phenomena for the WO_3-V_2O_5 varistors. 相似文献
163.
We have studied the kinetic behaviours of irreversible aggregation-annihilation models with cluster removals. In the models, an irreversible aggregation reaction occurs between any two clusters of the same species and an irreversible annihilation reaction occurs simultaneously between two different species; meanwhile, the clusters of large size are gradually removed from the system. In a mean-field limit, we obtain the general solutions of the cluster-mass distributions for the cases with an arbitrary removal probability. We found that the cluster-mass distribution of either species satisfies a generalized or modified scaling form. The results also indicate that the evolution behaviours of the systems depend strongly on the details of the reaction events. 相似文献
164.
NMR analogue of the generalized Grover‘s algorithm of multiple marked states and its application 总被引:3,自引:0,他引:3
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The generalized Grover's algorithm for the case in which there are multiple marked states is demonstrated on a nuclear magnetic resonance (NMR) quantum computer. The Walsh-Hadamard transform and the phase inversion are all replaced. NMR analogues of Einstein-Podolsky-Rosen states (pseudo-EPR states) are synthesized using the above algorithm. 相似文献
165.
Using expansions in terms of the Jacobi elliptic cosine function and third Jacobi elliptic function, some new periodic solutions to the generalized Hirota-Satsuma coupled KdV system are obtained with the help of the algorithm Mathematica. These periodic solutions are also reduced to the bell-shaped solitary wave solutions and kink-shape solitary solutions. As special cases, we obtain new periodic solution, bell-shaped and kink-shaped solitary solutions to the well-known Hirota-Satsuma equations. 相似文献
166.
The effect of the Bloch-Siegert shift on a strongly driven transition is studied in a three-level double-resonance configuration and the result is presented in this paper. We show that when a resonantly driven transition is probed to a third level, the Bloch-Siegert shift leads to an asymmetric Autler-Townes doublet. An important conclusion is that the asymmetry depends only on the driving field intensity, in contrast to a previous study where it is reported that the asymmetry depends not only on the driving field intensity but also on the characteristics of the three-level system. Our result implies an alternative way of measuring the Bloch-Siegert shift. 相似文献
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169.
研究了在含水量 90 %的非离子型微乳液——乳化剂 op/正丁醇 /正庚烷 /水中 ,在室温下用 5- Br- PADAP与 Co( )的显色反应进行 ,分光光度法测定钴 ,配合物最大吸收波长在 588nm,摩尔吸光系数达 1 .1 3*1 0 5 L· mol-1· cm-1 ,与相同含水量的乳化剂 OP胶束体系相比 ,本法测定的灵敏度明显提高 .Co含量 0~ 30μg/ 2 5ml范围符合比耳定律 相似文献
170.
Dr. Peng Gao Dr. Zihao Cui Dr. Xiaolei Liu Dr. Yaqiang Wu Dr. Qianqian Zhang Prof. Zeyan Wang Prof. Zhaoke Zheng Prof. Hefeng Cheng Prof. Yuanyuan Liu Prof. Qing Li Prof. Baibiao Huang Prof. Peng Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(50):e202201095
Lead halide perovskite has triggered a lot of research due to its superior optical properties. However, halide perovskite materials have poor environmental stabilities and are easily affected by external factors such as water and heat, resulting in structural decomposition and performance failure. Contrary to this commonplace concept, it is found that CsPbBr3 (CPB) can convert to CsPb2Br5 (CP2B5) partially when meeting a small amount of water, and the CsPbBr3@CsPb2Br5 (CPB@CP2B5) composite is synthesized by an in situ method accordingly. The CPB@CP2B5 composite shows an enhanced catalytic performance compared with pure CPB, as well as a dramatically synergistic effect of photo and thermal for catalytic CO2 hydrogenation. The CO production rate of CPB@CP2B5 is determined as 69 μmol g−1 h−1 under light irradiation at 200 °C, which is 156.8 and 43.4 times higher than that under pure photo (0.44 μmol g−1 h −1) and pure thermal (1.59 μmol g−1 h −1) condition, respectively. Meanwhile, the CPB@CP2B5 sample is also stable, which shows no significant decline in the catalytic activity during 8 cycles of repeated experiments. The probable mechanism is explored by utilizing a series of in situ characterizations. 相似文献