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41.
Yongbo Bian Jin Guo Changzheng Gao Chunguang Li Hong Li Jia Wang Bin Cui Xiaofeng He Chao Li Na Li Guoqiang Li Qiang Zhang Xueqiang Zhang Jibao Meng Yusheng He 《Physica C: Superconductivity and its Applications》2010,470(15-16):617-621
This paper presents a miniaturized high performance high temperature superconducting (HTS) microwave receiver front-end subsystem, which uses a mini stirling cryocooler to cool a high selective HTS filter and a low noise amplifier (LNA). The HTS filter was miniaturized by using specially designed compact resonators and fabricating with double-sided YBCO films on LAO substrate which has a relatively high permittivity. The LNA was specially designed to work at cryogenic temperature with noise figure of 0.27 dB at 71 K. The mini cryocooler, which is widely used in infrared detectors, has a smaller size (60 mm × 80 mm × 100 mm) and a lighter weight (340 g) than the stirling cryocoolers commonly used in other HTS filter subsystem. The whole front-end subsystem, including a HTS filter, a LNA, a cryocooler and the vacuum chamber, has a size of only φ120 mm × 175 mm and a weight of only 3.3 kg. The microwave devices inside the subsystem are working at 71.8 K with a consumed cooling power of 0.325 W. The center frequency of this subsystem is 925.2 MHz and the bandwidth is 2.7 MHz (which is a fractional bandwidth of 0.2%), with the gain of 19.75 dB at center frequency and the return loss better than ?18.11 dB in the pass band. The stop band rejection is more than 60 dB and the skirt slope is exceeding 120 dB MHz?1. The noise figure of this subsystem is less than 0.8 dB. This front-end subsystem can be used in radars and communication systems conveniently due to it’s compact size and light weight. 相似文献
42.
We obtain a classification for the fundamental groups of closed $n$ -manifolds of positive sectional curvature which admit an isometric $T^k$ -action with $k \ge \frac{n}{6}+1 (n \ne 11, 15)$ . 相似文献
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Zhenjiang Qiu Mingxiang Zhu Lu Zheng Jingya Li Dapeng Zou Yangjie Wu Yusheng Wu 《Tetrahedron letters》2019,60(19):1321-1324
An efficient protocol for the synthesis of α-benzyl azetidines starting from benzylboronic acid pinacol ester derivatives and 3-iodoazetidine was developed. A wide range of α-benzyl azetidine derivatives were obtained in moderate to good yields with high regioselectivity (>99%). 相似文献
45.
In this paper, we demonstrated an integrated digital image processing framework that is training‐free for high throughput beads or biological cells detection and enumeration by the bead aggregation splitting algorithm. By making contour extraction processing, the aggregated beads can be clearly split for precise counting. It can be potentially embedded on‐chip in a miniaturized medical equipment to automatically adjust illumination condition and de‐noise. This study demonstrates that the existing hematological analysis can be updated from manual classification and counting by high‐speed and precise machine‐based programs. 相似文献
46.
In the current field of biomedical engineering, the research on implanted antennas has attracted more and more attention. This paper presents a flexible terrestrial radiating antenna with circular polarization characteristics that satisfy various requirements for biomedical implantable antennas. The new type of flexible material is adopted and a novel model is proposed. The square ground with small gap is implemented in the proposed antenna. The passive components can match the impedance and meet the requirements of the circular polarization wave. Simulation is carried out in a single layer tissue model to estimate the performance of the antenna and compared with multilayer tissue model. In addition, the flexible circularly polarized antenna has low profile characteristics and a wide axial ratio bandwidth of 250 MHz, ranging from 2.28 to 2.53 GHz. This paper uses pork to simulate single‐layer and multi‐layer tissue model. The flexible circular polarized antenna prototype is placed in the organization model for performance simulation test, and the measurement impedance bandwidth of 500 MHz is realized in the industrial scientific medical frequency band of 2.4–2.48 GHz. 相似文献
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铝卟啉是一类土壤环境友好的金属卟啉,尽管早在1978年Inoue就已经发现它可以催化CO2和环氧丙烷的共聚反应,但是该催化体系一直面临催化活性低、聚合物相对分子质量低等难题。 本文通过改变铝卟啉催化剂配体中苯环上取代基的种类和位置,制备出中心金属电子环境差异化的铝卟啉,并以双三苯基膦氯化铵(PPNCl)为助催化剂,探讨其对CO2与环氧丙烷的共聚反应的催化行为。 结果表明,当铝卟啉中苯环上2,4位同时被Cl-取代后,在90 ℃和3 MPa压力下,转化频率(TOF)达到2672 h-1。 当利用离去能力较强的对甲苯磺酸基团(OTs-)作为铝卟啉的轴向配体,可以合成出数均相对分子质量达1.84×105的脂肪族聚碳酸酯。 相似文献
48.
Qixun Guo Yusheng Zhao Chao Jiang Wendy L. Mao Zhongwu Wang 《Solid State Communications》2008,145(5-6):250-254
Sm2O3 was compressed at room temperature up to 44.0 GPa and then decompressed back to ambient pressure. In situ X-ray diffraction was used to monitor the structural changes in the sample. A cubic to hexagonal phase transformation was observed in Sm2O3 for the first time. After decompression back to ambient pressure, the hexagonal phase was not quenchable and transformed to a monoclinic phase. Ab initio Density- Functional-Theory (DFT) calculations were performed to obtain theoretical data for comparison with the experimental results and elucidation of the transformation mechanism. A possible phase transformation mechanism that is consistent with the experimental results and theoretical calculations is proposed. 相似文献
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