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61.
高清4G公网防爆摄像仪系统是为石油化工等高危防爆环境研制的便携移动防爆摄像系统。如何在高清4G模块高发射功率、多储能元件的前提下实现设备的总体防爆指标以满足国家标准是本文解决的重点问题。基于防爆理论,通过提高设备防爆电容设计门限和降低电路容值设计的电容管理手段,对整体设备的储能元件进行了极限防爆限制,优化设计了4G-LTE无线摄像模块的最低储能电容解决方案;利用双半波振子天线列阵技术实现天线设备的发射功率限制硬件保护,采用软件保护手段实现双重防爆保护,从设计原理上保证了研发的高清4G摄像仪满足《GB 3836.1-2000》防爆要求。在保证防爆性能和设备功能的前提下,设备电容容量降低了50%,设备远场电场强度9%。 相似文献
62.
本文提出了一种基于65nm CMOS标准工艺、采用粗调和细调相结合的低噪声环形压控振荡器。论文分析了环形振荡器中的直接频率调制机理,并采用开关电容阵列来减小环形压控振荡器的增益从而抑制直接频率调制效应。开关电容采用电容密度较高的二维叠层MOM电容使该压控振荡器与标准的CMOS工艺兼容。所设计压控振荡器的频率范围为480MHz~1100MHz,调谐范围为78%,测试得到输出频率为495MHz时的相位噪声为-120dBc/Hz@1MHz。该压控振荡器在1.2V的偏压下的功耗为3.84mW,相应的优值(FOM)为-169dBc/Hz。 相似文献
63.
Zhang Xiumiao 《电子科学学刊(英文版)》1992,9(3):265-269
When a linear voltage ramp is applied to the gate of a MOS capacitor, a capacitancetime (C-t) transient is observed. The MOS capacitor is biased into strong inversion before applying the voltage ramp in order to eliminate
surface generation. FromC-t transient curve obtained experimentally the minority carrier generation lifetime in semiconductor can be determined. The
experimental results show that for the same sample the lifetimes extracted fromC-t curves under varying voltage sweep rates are close each other, and they are consistent with the lifetimes extracted by saturation
capacitance method. 相似文献
64.
65.
Oligothioethers 4-RC6H4(SC6H4-4)nX (n = 1-3; X = Br, I; R = NO2; X = Br; R = MeO. n = 1 and 2; X = I; R = MeO. n = 4; X = Br; R = NO2) have been prepared through a process involving (i) palladium-catalyzed C-S coupling between 4-RC6H4(SC6H4-4)n−1I and 4-BrC6H4SH to give 4-RC6H4(SC6H4-4)nBr and (ii) copper-catalyzed replacement of Br by I. 相似文献
66.
Dr. Ko Sato Dr. Hiroshi Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(36):9422-9428
Lignans are a group of polyphenolic phytochemicals that possess a large spectrum of chemical structures and biological activities. Here the syntheses of lignans – anwulignan, burseran, dehydroxycubebin, ruburisandrin B, and sesamin – are achieved based on a borate-mediated one-pot sequential Suzuki-Miyaura coupling of cis- and trans-fused bicyclic boranes, which were prepared by diastereoselective cyclic hydroboration of exo-cyclic diene with cyclopentyl- and thexylboranes, respectively. A one-pot sequential Suzuki-Miyaura coupling of each cyclic borate with various aryl bromides initiated by activation of the cyclic borane with the carbon nucleophile provided 2,3-dibenzylbutane derivatives with different aromatic substituents. Finally, the syntheses of naturally occurring lignans were accomplished in several steps from the products of Suzuki-Miyaura coupling. 相似文献
67.
68.
石墨烯由于拥有超高比表面积和超高电导率而被作为电化学电容器材料广泛研究.本文采用树脂为碳源,通过一种方便快捷的树脂交换法制备一种具有高比表面积的多级孔三维石墨烯(3DG).经过此种方法的催化、造孔、热处理等主要工艺步骤后,可显著增加石墨烯材料的小、介孔数量,从而提高材料的电化学性能.通过BET测试表明,3DG的比表面积可达2400 m2/g,孔体积达到2.0 cm3/g.以3DG作为正负极材料制备高比能量高功率型锂离子电容器(3DG-LIC),可使3DG-LIC的工作电压从传统超级电容器的2.5 V扩展到4.0 V,能量密度也从20 Wh/kg提高到105 Wh/kg.另外,相同的化学和微观结构能很好地平衡正负极的容量及速率,使高比能量高功率的3DG-LIC具有更宽阔的应用领域. 相似文献
69.
Giulia Marsico Barbara A. Pignataro Marco Masi Antonio Evidente Francesca Casella Maria Chiara Zonno Jun-Hyung Tak Jeffrey R. Bloomquist Stefano Superchi Patrizia Scafato 《Tetrahedron》2018,74(28):3912-3923
The first asymmetric total synthesis of both enantiomers of the natural products colletorin A and colletochlorin A is presented. The proposed methodology is based on the coupling reaction between highly substituted aromatic Gilman cuprates and optically active allyl bromides, in turn obtained by Sharpless asymmetric dihydroxylation. The latter ensured a high degree of regio- and stereocontrol in the enantioselective step of the synthesis. The same synthetic strategy has been also applied for the preparation of differently halogenated synthetic analogues of colletochlorin A in high enantiomeric purity. The enantioselective synthesis of colletorin A and colletochlorin A allows to reliably assign their absolute configuration. Preliminary assessment of their herbicidal and insecticidal properties evidence the possibility to modulate the bioactivity of these compounds, highlighting its dependence on both the absolute stereochemistry and the halogen nature. 相似文献
70.
Talat Baran 《高分子科学杂志,A辑:纯化学与应用化学》2018,55(3):280-287
To maintain catalytic performance of any catalyst for a long time, the selection of support material is a very important parameter for heterogeneous catalytic systems, and this performance makes the catalyst valuable. In view of its low cost and availability, silica can be considered as a good support material for transition metal ions in the cross coupling reactions. Therefore, this study describes i) silica-gel based palladium catalyst with a long-term catalytic performance, ii) rapid, simple, economic, and green procedure which was developed for Suzuki reactions. The catalyst showed superior reusability (ten runs) and catalytic efficiency against coupling reactions under mild conditions (50°C, 5 min and air atmosphere). Moreover, the catalyst gave partially good reaction yields with aril chlorides which have poor activity in coupling reactions. In addition, an excellent turnover number (TON: 66000) and frequency (TOF: 825000) were obtained using very small catalyst loading (1.5 × 10?3 mol %). This paper concludes that silica-gel based Pd(II) catalyst and the protocol of synthesis of biaryls were suitable for coupling reactions. 相似文献