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231.
We investigate the transmission of electrons through a quantum point contact by using a quasi-one-dimensional model with an extra local bound state staying below the band bottom. While the complete transmission in lower channels gives rise to plateaus of conductance at multiples of 2e2/h, the electrons in the lowest channel are scattered by the local bound state when it is singly occupied. This scattering produces a wide anti-resonant zero-transmittance for singlet formed by tunneling and local electrons, and has no effect on triplets, leading to an exact 0.75(2e2/h) shoulder prior to the first 2e2/h plateau. While at low temperature, the formation of Kondo cloud screens magnetic moment of the local bound state and reduces the scattering to the singlet channel, complementing the shoulder from 0.75 to 1. 相似文献
232.
介绍了一种采用前置微型电机的新型推拉式超声内窥镜的研制方法.在该内镜系统中,采用FPGA实现成像处理功能,运用编码激励技术以提高系统的信噪比和探测深度,使用了微型前置探头取代了目前商用超声内镜中所采用的钢丝连接以驱动换能器进行旋转扫描.该仪器在300 h的连续工作测试中能够正常运行.相较模拟成像系统,数字系统将模数转换置于信号处理的最前端,从而能够保留回声的更多信息.这使得编码激励、数字式正交解调系统获得更高的成像质量.将电机前置于探头附近,能够较外部导线牵引旋转方式获得更大的旋转稳定性、更高的超声图像质量和更长的使用寿命. 相似文献
233.
Qian-Kui Zhang Shu-Yu Sun Dr. Ming-Yue Zhou Li-Peng Hou Jia-Lin Liang Shi-Jie Yang Dr. Bo-Quan Li Dr. Xue-Qiang Zhang Prof. Jia-Qi Huang 《Angewandte Chemie (International ed. in English)》2023,62(42):e202306889
The stability of high-energy-density lithium metal batteries depends on the uniformity of solid electrolyte interphase (SEI) on lithium metal anodes. Rationally improving SEI uniformity is hindered by poorly understanding the effect of structure and components of SEI on its uniformity. Herein, a bilayer structure of SEI formed by isosorbide dinitrate (ISDN) additives in localized high-concentration electrolytes was demonstrated to improve SEI uniformity. In the bilayer SEI, LiNxOy generated by ISDN occupies top layer and LiF dominates bottom layer next to anode. The uniformity of lithium deposition is remarkably improved with the bilayer SEI, mitigating the consumption rate of active lithium and electrolytes. The cycle life of lithium metal batteries with bilayer SEI is three times as that with common anion-derived SEI under practical conditions. A prototype lithium metal pouch cell of 430 Wh kg−1 undergoes 173 cycles. This work demonstrates the effect of a reasonable structure of SEI on reforming SEI uniformity. 相似文献
234.
Wen-Dong Song Shi-Jie Li Li-Li Ji Shao-Wei Tong Dong-Liang Miao 《Journal of Cluster Science》2012,23(2):585-596
Two new isostructural coordination polymers, namely, [Ln(nbtc)·2H2O] n [Ln = Eu (1), Tm (2)] (H3nbtc = 5-nitrobenzene-1,2,3-tricarboxylic acid), have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, and single crystal X-ray diffraction. Both compounds are sandwich-like 2D layered network built by the 1D Ln-carboxylate chains and nbtc3? linkers, displaying the same 3D supramolecular network via intermolecular hydrogen bonds. The photoluminescence and lifetime of 1 in the solid state has also been investigated. 相似文献
235.
236.
For the organic magnetoresistance(OMAR) effect, we suggest a spin-related hopping of carriers(polarons) based on Marcus theory. The mobility of polarons is calculated with the master equation(ME) and then the magnetoresistance(MR)is obtained. The theoretical results are consistent with the experimental observation. Especially, the sign inversion of the MR under different driving bias voltages found in the experiment is predicted. Besides, the effects of molecule disorder,hyperfine interaction(HFI), polaron localization, and temperature on the MR are investigated. 相似文献
237.