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991.
将矩形交错双栅结构作为慢波电路并提出与之配套的过渡结构和输出耦合器,设计了利用带状电子注工作在W波段的返波振荡器。提出的过渡结构和耦合器解决了该类直波导型器件的信号传输衰减大、反射强等难题。相对于传统圆形电子注器件,该器件得到了较大的功率提升。利用三维粒子模拟计算的方法,在电流12 mA时通过调节工作电压,在92~98 GHz频带内得到了数W的稳定平均功率输出,信号中心频率非常接近设计频率,且单色性好,谐波分量小。 相似文献
992.
993.
文章以一个设计性实验课程设计为例,积极地融合现代信息技术,讨论如何结合现代信息技术的大学物理设计性及研究性实验课程,培养学生创新意识。 相似文献
994.
An original ultrasound (US) directly intensified photocatalytic reactor was designed to degrade azo dye pollutant methyl orange (MeO) using Degussa TiO(2) as the photocatalyst. The sonolytic, photocatalytic and sonophotocatalytic degradation of MeO in the new reactor and the synergistic effect between sonolysis and photocatalysis were investigated. Effects of operation parameters i.e., US power, TiO(2) dosage, liquid circulation velocity and air flow rate on degradation efficiency were investigated and optimized. The results showed that all parameters have optimal values for the sonophotocatalytic degradation of MeO, and the optimum conditions for the new process are US power 600 W, TiO(2) dosage 3g/L, liquid circulation velocity 4.05×10(-2) m/s and air flow rate 0.2 L/min. Under the optimum conditions, 91.52% MeO had been degraded within 1h, and the combination of sonolysis and TiO(2) photocatalysis exhibited an obvious synergetic effect. 相似文献
995.
Yu Zhao Li-ping Xu Jun Tong Yong-qiang Li Li-xia Xiong Fang Li Li-na Peng Zheng-ming Li 《Molecular diversity》2012,16(4):711-725
In searching for environmentally benign insecticides with high activity, low toxicity and low residue, two series of novel anthranilic diamide containing methyl ether and isopropyl ether group were designed and synthesized. All of the compounds were characterized by 1H NMR spectroscopy, 13C NMR spectroscopy and elemental analysis. The single crystal structure of 19j was determined by X-ray diffraction. The insecticidal activities of the new compounds were evaluated. The results showed that some compounds exhibited excellent insecticidal activities against Lepidoptera pests. Among this series, compound, 18l showed 100?% larvicidal activity against Mythimna separate Walker, Plutella xylostella Linnaeus and Laphygma exigua Hubner at the test concentration, which was equal to the available chlorantraniliprole. 相似文献
996.
The monolayer Al2O3:Ag thin films were prepared by magnetron sputtering. The microstructure and optical properties of thin film after annealing
at 700 °C in air were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy,
and spectrophotometer. It revealed that the particle shape, size, and distribution across the film were greatly changed before
and after annealing. The surface plasmon resonance absorption and thermal stability of the film were found to be strongly
dependent on the film thickness, which was believed to be associated with the evolution process of particle diffusion, agglomeration,
and evaporation during annealing at high temperature. When the film thickness was smaller than 90 nm, the film SPR absorption
can be attenuated until extinct with increasing annealing time due to the evaporation of Ag particles. While the film thickness
was larger than 120 nm, the absorption can keep constant even after annealing for 64 h due to the agglomeration of Ag particles.
On the base of film thickness results, the multilayer Al2O3:Ag solar selective thin films were prepared and the thermal stability test illustrated that the solar selectivity of multilayer
films with absorbing layer thickness larger than 120 nm did not degrade after annealing at 500 °C for 70 h in air. It can
be concluded that film thickness is an important factor to control the thermal stability of Al2O3:Ag thin films as high-temperature solar selective absorbers. 相似文献
997.
F. Song Å. Monsen Z.S. Li E.-M. Choi J.L. MacManus-Driscoll J. Xiong Q.X. Jia E. Wahlström J.W. Wells 《Surface science》2012,606(23-24):1771-1776
The surface and near-surface chemical composition of BiFe0.5Mn0.5O3 has been studied using a combination of low photon energy synchrotron photoemission spectroscopy, and a newly developed maximum entropy finite element model from which it is possible to extract the depth dependent chemical composition. In the uppermost few unit cells, an overabundance of Bi, and a deficiency of Fe and Mn are observed. In deeper layers, the measurements are consistent with bulk-like stoichiometry.Additionally, a definitive identification of all the observed species together with their abundance and depth dependence is given, and the mixed Fe and Mn valencies are estimated. In addition to the expected bulk valencies Mn3 + and Fe3 +, some Fe2 + and a small amount of Mn4 + are also observed. The maximum entropy finite element model demonstrated here is also discussed in more general terms and its potential application to the broader field of perovskite thin films is made apparent. 相似文献
998.
光热敏折变玻璃及其布拉格体光栅特性研究 总被引:3,自引:1,他引:2
采用高温二次化料的方法制备了一种SiO2-Al2O3-ZnO-Na2O(F、Br)玻璃体系的光热敏折变(PTR)玻璃,通过紫外曝光、透射率光谱、X射线衍射(XRD)和差热分析等方法研究了其光热敏析晶机理。研究表明,PTR玻璃的光敏区为280~350nm,工作区为400~2700nm,最佳成核温度和析晶温度分别为490℃和595℃,析晶组分为NaF晶体。采用双光束干涉方法与"两步法"的热处理工艺在PTR玻璃中制备了周期为1000mm-1的布拉格体光栅,光栅的相对衍射效率达到91%,并验证了制备的布拉格体光栅具有角选择滤波能力。 相似文献
999.
A reliable LC-MS method has been applied for the separation and identification of major constituents of the rhizome of Smilacis glabrae. Identification of the constituents was carried out by interpretation of their retention time, and MS and MS/MS data, especially by comparing these with Sarcandra glabra under the same LC-MS conditions, as well as the data provided by the literature. Thirty-three compounds, including catechin derivatives, flavanonols, phenolic acid derivatives and phenylpropanoid glycosides were either identified or tentatively characterized. Among them, compound 12 was deduced to be a new phenylpropanoid-substituted catechin. Fragmentation behaviors of the three major categories of compounds were also investigated. This UPLC-PDA/ESI-MS(n) method was effective for the separation and identification of the constituents and could be the basis for the comprehensive quality control of Smilacis glabrae. 相似文献
1000.
Frank Seela Hui Mei Hai Xiong Simone Budow Henning Eickmeier Hans Reuter 《Acta Crystallographica. Section C, Structural Chemistry》2012,68(10):o395-o398
The title compound [systematic name: 4‐amino‐1‐(2‐deoxy‐β‐d ‐erythro‐pentofuranosyl)‐5‐ethynylpyrimidin‐2(1H)‐one], C11H13N3O4, shows two conformations in the crystalline state. The N‐glycosylic bonds of both conformers adopt similar conformations, with χ = −149.2 (1)° for conformer (I‐1) and −151.4 (1)° for conformer (I‐2), both in the anti range. The sugar residue of (I‐1) shows a C2′‐endo envelope conformation (2E, S‐type), with P = 164.7 (1)° and τm = 36.9 (1)°, while (I‐2) shows a major C3′‐exo sugar pucker (C3′‐exo‐C2′‐endo, 3T2, S‐type), with P = 189.2 (1)° and τm = 33.3 (1)°. Both conformers participate in the formation of a layered three‐dimensional crystal structure with a chain‐like arrangement of the conformers. The ethynyl groups do not participate in hydrogen bonding, but are arranged in proximal positions. 相似文献