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81.
本文提出了一种应用于双通道卫星导航接收机的高效率低噪声电源解决方案,主要包括降压型DC-DC转换器和低压差稳压器。为了获得更好的噪声抑制和抗干扰性能,应用脉冲宽度调制(PWM)作为DC-DC转换器的控制方式。提出了一种改进的低功耗PWM控制电路,通过周期性的关断跨导放大器,将转换器的平均静态功耗降低了一半,并且具有较高的工作频率。针对双通道接收机的特点,对输出级功率管的尺寸进行了优化,使效率最优。另外,提出了一种基于限流原理的新型软启动电路,无须使用片外大电容或数模转换器,降低了设计复杂度。电路使用180nm CMOS工艺流片,测试结果显示,DC-DC转换器在2MHz的工作频率下拥有最高93.1%的转换效率,整个双通道接收机在3.3V电源供电下仅消耗电流20.2mA。 相似文献
82.
Man-Li Cao Jun-Ling Zhu Zhong-Lan Zhi Bao-Hui Ye Su-Yang Yao Xiu-Lian Zhang 《中国化学》2021,(6):1483-1490
Main observation and conclusion
Chiral-at-metal strategy was developed to resolve the essential sulfoxide pharmaceutical intermediates R-modafinil acid and its ... 相似文献
83.
Abstract Different methods for the determination of the local field anisotropy in liquid crystals are analysed and the problems resulting from their application are outlined. One such method, namely that based on the comparison of the polarization of resonance Raman scattering and absorption bands is studied in more detail. The method is applied to determine the structural anisotropy for the 4-n-pentyl-(4′-cyanophenyl) derivatives of benzene, cyclohexane and bicyclooctane. To account for the difference between the optical properties of the probe and of the solvent at the wavelength of the scattered light the local field factor is treated theoretically within the framework of an anisotropic continuous dielectric medium. 相似文献
84.
Eleven triazolyl substituted tetrahydrobenzofuran derivatives were synthesized in high yields as novel H+/K+‐ATPase inhibitor via one‐pot CuI‐catalyzed three‐component click reaction of azide, secondary amine and 3‐bromopropyne under mild conditions in water. Their structures were characterized by NMR, IR, ESI‐MS, elemental analysis and single‐crystal X‐ray diffraction analysis. Most of the target compounds exhibited better H+/K+‐ATPase inhibitory activity than commercial omeprazole with IC50 values less than 15 µmol·L?1. The initial structure‐activity analysis suggested that the triazole substituted by cycloalkyl, aromatic ring or O‐containing side‐chain seemed to be beneficial for enhancing the activity. 相似文献
85.
Özlem Yeşiltaş 《Central European Journal of Physics》2013,11(12):1674-1679
In this paper, we have provided a matrix Hamiltonian model for honeycomb lattices and subsequently obtained the dispersion relation. Furthermore, we have constructed the C operator for the given non-Hermitian Hamiltonian model. The quadratic surfaces are sketched and the quantum Brachistochrone problem is discussed for the given honeycomb lattice model. 相似文献
86.
Yunfeng Bao Hai Zou Nengcong Yang Gao Li Fuxiang Zhang 《Journal of Energy Chemistry》2021,(12):358-363
Perovskite BaTaO2N (BTON) is one of the most promising photocatalysts for solar water splitting due to its wide visible-light absorption and suitable conduction... 相似文献
87.
An information hiding algorithm is proposed, which hides information by embedding secret data into the palette of bitmap resources of portable executable (PE) files. This algorithm has higher security than some traditional ones because of integrating secret data and bitmap resources together. Through analyzing the principle of bitmap resources parsing in an operating system and the layer of resource data in PE files, a safe and useful solution is presented to solve two problems that bitmap resources are incorrectly analyzed and other resources data are confused in the process of data embedding. The feasibility and effectiveness of the proposed algorithm are confirmed through computer experiments. 相似文献
88.
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90.
G. A. Zou S. Mansur S. C. Hu H. A. Aisa Kh. M. Shakhidoyatov 《Chemistry of Natural Compounds》2012,48(4):635-637
The novel pyrrole alkaloid alhagifoline A (1) together with the two known analogs pyrrolezanthine (2) and pyrrolezanthine-6-methyl ether (3) were isolated from the aerial part of Alhagi sparsifolia. Their structures were established based on spectral (HR-ESI-MS, 1 H and 13C NMR, 1 H–1 H COSY, HSQC, HMBC) data. Compounds 2 and 3 were isolated from the genus Alhagi for the first time. 相似文献