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1.
行波管栅控电子枪各组件尤其是阴极和栅网的热形变对行波管电子光学性能有着较大的影响。基于有限元分析方法,利用热力场耦合对栅控电子枪热形变问题进行了研究,结果表明:阳极的总形变量最大,最高处达0.28 mm;控制栅网、阴影栅、阴极及部分支撑结构向着阳极方向发生形变,由温升引起的形变不会使控制栅网和阴影栅发生接触或交叉,而阴极形变量较大时,阴极与阴影栅则存在接触的危险,这对电子枪的工作性能有很大的影响,甚至会使阴影栅烧坏。降低电子截获率,适当增加控制栅网和阴影栅的厚度,使用热传导率高、线膨胀系数低的材料,可以减小栅控电子枪各组件的热形变。 相似文献
2.
行波管栅控电子枪各组件尤其是阴极和栅网的热形变对行波管电子光学性能有着较大的影响。基于有限元分析方法,利用热力场耦合对栅控电子枪热形变问题进行了研究,结果表明:阳极的总形变量最大,最高处达0.28 mm;控制栅网、阴影栅、阴极及部分支撑结构向着阳极方向发生形变,由温升引起的形变不会使控制栅网和阴影栅发生接触或交叉,而阴极形变量较大时,阴极与阴影栅则存在接触的危险,这对电子枪的工作性能有很大的影响,甚至会使阴影栅烧坏。降低电子截获率,适当增加控制栅网和阴影栅的厚度,使用热传导率高、线膨胀系数低的材料,可以减小栅控电子枪各组件的热形变。 相似文献
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高重复频率、高平均流强的电子枪具有十分广泛的应用。设计了一台束团重复频率为325 MHz在CW模式工作的微波栅控高压型热阴极电子枪,并详细论述了该类型微波栅控电子枪的实验原理。在该类型电子枪的设计中,首先需要利用仿真模拟软件EGUN、POISSON(PoissonSuperfish)、GPT(General Particle Tracer)完成300 kV直流高压电子枪的结构设计,并进行束流动力学验证计算。为将微波馈入该直流电子枪的阴栅极之间,进行了该微波栅控电子枪的供电系统设计,完成了从射频功率源到同轴热阴极的阻抗匹配方案,设计了一种325 MHz双模式同轴供电器件,并进行了验证与分析。 相似文献
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为了对双极器件在电离辐射环境下的损伤机理及加固技术进行深入的研究,对设计制作的不同工艺类型的栅控横向PNP双极晶体管进行了60Co-γ低剂量率辐照试验.结果表明:1)栅控双极晶体管的辐射特性具有很强的工艺相关性,钝化层的存在对于双极晶体管的辐射响应具有很大影响,有钝化层的器件在电离辐射环境中会产生更多的界面态,其抗辐射能力大大减弱;2)针对国产栅控横向PNP晶体管在低剂量率辐照时会发生峰值电流展宽效应,文中对展宽效应潜在机理进行了分析,并针对展宽效应提出了新的分离方法.这不但对设计抗辐射加固器件提供了依据,而且为进一步深入研究双极器件的低剂量率辐射损伤增强效应提供了强有力工具. 相似文献
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锚头的受力情况对整个锚杆的安全性有着重要影响。为了实时反映锚头的受力状态,将2只光纤Bragg光栅沿45°粘贴在轮辐式结构锚头的两根对称辐条中点处表面上,形成轮辐式测力传感结构,辐条在压力作用下产生剪切变形,引起辐条表面的光纤Bragg光栅中心波长移位。通过对光纤Bragg光栅中心波长移位的测量,实现在锚头处锚杆轴向拉力的在线监测。锚头压力实验表明:光栅1的测力灵敏度为108.8pm/kN,线性度为0.042%FS;光栅2的测力灵敏度为115pm/kN,线性度为0.023%FS。 相似文献
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V. Sydorchuk S. Khalameida J. Skubiszewska-Zi?ba K. Wieczorek-Ciurowa 《Applied Surface Science》2010,257(2):446-450
Influence of mechanochemical activation on porous structure and surface properties of porous and non-porous silicas in air, water and ethanol has been studied. Milled samples have been investigated with help of nitrogen adsorption-desorption, mercury porometry, thermogravimetric analysis, FTIR and ESR spectroscopy. It has been revealed that destruction of porous structure of silicagel at dry milling and, on the contrary, formation of porous silica from non-porous powders (aerosils) during treatment in liquid media occurs. 相似文献
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热退火是多孔低介电常数薄膜制备过程中的重要一环, 对薄膜结构及性能具有重要影响. 本文以四乙氧基硅烷和双戊烯为前驱体, 采用等离子体增强化学气相沉积方法制备了SiCOH薄膜, 对其进行了氮气氛围下的热退火处理, 分析了热退火对薄膜结构与性能的影响, 探究了退火过程中薄膜结构变化的可能的反应机理. 傅里叶变换红外光谱和固体核磁共振谱结果表明, 沉积薄膜是一种有机无机杂化薄膜. 退火过程中, 薄膜中的-CH2, -CH3等有机组分被分解除去, 形成了以稳定的Si-O-Si等无机组分为骨架的多孔结构, 并通过氮气吸附/脱附等温线测试得到了验证. 在此期间, 薄膜骨架微结构亦发生一系列调整, C=C, Si-C含量增加, Si、O、C等元素间发生进一步键合. C=C 含量的提高, 使得薄膜的消光系数和漏电流密度增大. 实验证明, 退火后薄膜具有低折射率、低介电常数特性, 是一类具有优异的介电性能和力学性能的材料, 作为芯片后端互连层间介质具有极大的应用潜力. 相似文献
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Sebastián Feliu Jr. C. MaffiotteA. Samaniego Juan Carlos GalvánVioleta Barranco 《Applied Surface Science》2011,257(20):8558-8568
The purpose of this study has been to advance in knowledge of the chemical composition, structure and thickness of the thin native oxide film formed spontaneously in contact with the laboratory atmosphere on the surface of freshly polished commercial AZ31 and AZ61 alloys with a view to furthering the understanding of protection mechanisms. For comparative purposes, and to more fully describe the behaviour of the native oxide film, the external oxide films formed as a result of the manufacturing process (as-received condition) have been characterised. The technique applied in this research to study the thin oxide films (thickness of just a few nanometres) present on the surface of the alloys has basically been XPS (X-ray photoelectron spectroscopy) in combination with ion sputtering. Corrosion properties of the alloys were studied in 0.6 M NaCl by measuring charge transfer resistance values, which are deduced from EIS (electrochemical impedance spectroscopy) measurements after 1 h of exposure. Alloy AZ61 generally showed better corrosion resistance than AZ31, and the freshly polished alloys showed better corrosion resistance than the alloys in as-received condition. This is attributed to a combination of (1) higher thickness of the native oxide film on the AZ61 alloy and (2) greater uniformity of the oxide film in the polished condition. The formation of an additional oxide layer composed by a mixture of spinel (MgAl2O4) and MgO seems to diminish the protective properties of the passive layer on the surface of the alloys in as-received condition. 相似文献
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S. Bhattacharjee S. M. Jaya 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,49(3):305-311
The influence of correlation and temperature on the electronic structure of bulk and
thin film GdN
has been studied using the s-f model, which combines
the one electron band structure with a many body procedure.
The tight binding linear muffin tin orbital (TB-LMTO) method was used to obtain
the one electron band structure of
the system. The s-f exchange coupling constants
for each band were obtained from the spin polarized band structure of
the system using a mean field model.
Correlation effects are found to be present in the system. However they
are not sufficiently strong to cause a correlation induced splitting in the
spectrum. Some bands of the thin films of GdN exhibit splitting at T=Tc
and it is due to the combined effect
of correlation and temperature. The conduction bands of both the bulk and
the thin films of GdN exhibit a red shift with respect to temperature. 相似文献
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Elena I. Suvorova Oleg V. Uvarov Alexey V. Ovcharov Igor A. Karateev Alexandr L. Vasiliev Vladimir A. Skuratov 《哲学杂志》2013,93(35):3127-3142
ABSTRACTThe response of Y2O3 nanoprecipitates in a 1-µm YBa2Cu3O7-x layer from a superconducting wire Ag/YBCO/buffer metal oxides/Hastelloy to 107?MeV Kr and 167?MeV Xe ion irradiation was investigated using a combination of transmission electron microscopy, diffraction and X-ray energy-dispersive spectrometry. The direct observation of the radiation-induced tracks in Y2O3 nanocrystals is reported for the first time to the authors’ best knowledge. Structureless damaged regions of 5–9?nm (average 8?nm) in diameter were observed in Y2O3 nanocrystals when the electronic stopping power Se was about or higher than 4.7 keV/nm. This value of Se is the upper estimate of the minimum electronic stopping power to create damage in yttria nanocrystals. The electron diffraction patterns, high-resolution transmission electron microscopy, high-resolution scanning transmission electron microscopy, Fourier transform patterns from areas extending a few nanometres around the tracks show that yttria and YBCO keep their respective cubic and orthorhombic pristine structures. 相似文献
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Hongwei Liu Dongjiang Yang Eric R. Waclawik Xuebin Ke Zhanfeng Zheng Huaiyong Zhu Ray L. Frost 《Journal of Raman spectroscopy : JRS》2010,41(12):1792-1796
A detailed study on the structural deformation of trititanate nanofibers after the adsorption of divalent strontium (Sr) and barium (Ba) cations was conducted by using Raman spectroscopy, X‐ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that the Raman bands at 309 cm−1 corresponding to very long Ti O bonds (2.2 Å) and at 883 cm−1 corresponding to the very short Ti O bonds (1.7 Å) decreased in intensity after the adsorption of Ba2+ and Sr2+ cations. Additionally, the band at 922 cm−1 corresponding to an intermediate length Ti O bond was observed to weaken with the adsorption of divalent cations, indicating that the TiO6 octahedra in Na2Ti3O7 are more regular. These results suggest that the active sodium (Na+) cations in Na2Ti3O7 should be located at the corner of the TiO6 octahedral slabs, i.e. the plane (003). This was further confirmed by a large decrease of diffraction intensity of the plane (003) observed in the XRD pattern. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Effect of local structure on electron paramagnetic resonance spectra for trigonal [Cr(H2O)6]3+coordination complex in the sulfate alums series: a ligand field theory study 下载免费PDF全文
A simple theoretical method is introduced for studying the interrelation between electronic and molecular structures.By diagonalizing the 120 × 120 complete energy matrices,the relationships between zero-field splitting(ZFS) parameter D and local distortion parameter △θ for Cr 3+ ions doped,separately,in α-and β-alums are investigated.Our results indicate that there exists an approximately linear relationship between D and △θ in a temperature range 4.2-297 K and the signs of D and △θ are opposite to each other.Moreover,in order to understand the contribution of spin-orbit coupling coefficient ζ to ZFS parameter D,the relation between D and ζ is also discussed. 相似文献
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The full wavevector and frequency dependent complex dielectric function for two component classical and quantum rare hot plasmas
have been derived. The real part of dielectric function is obtained in the form of a series. Difference between quantum and
classical real and imaginary parts of dielectric function have been brought out by making explicit calculations. The quantum
nature of the plasma brings about significant changes in both parts depending upon the magnitude of quantum parameter,R (= 8.93(λth)/λ).
Expressions for the dynamic structure factors for both two component classical and quantum plasma have been evaluated for
different values of the mass of the positive componentm
+, temperature T+ and wavevector k. It is found that the plasma exhibits well defined collective modes for certain values of |k| accompanied by varying disorder which depends upon the values of m+ as well as on |k| and T+. For the quantum case the collective modes are less well defined as compared to the corresponding classical case, thus proving
that quantum nature introduces inherent disorder in the system. But for both the cases, increase in temperature destroys collective
modes. Another feature is the appearance of a hump near Ω = 0 which becomes smaller and vanishes as the quantum parameter
is decreased.
Instability of plasma modes in the presence of constant electric field has also been worked out for the quantum case. 相似文献
20.
Wen-Yan Tian Xiao-Yu Kuang Mei-Ling Duan Rui-Peng Chai Cai-Xia Zhang 《Physica B: Condensed Matter》2009,404(21):3114-4336
A theoretical method for studying the inter-relation between electronic and molecular structure has been proposed based on the complete energy matrices for a d3 configuration ion in a tetragonal ligand-field. By means of this method, the local structure for Cr3+ ion doped in oxides TiO2 (anatase) and MgO has been determined. The calculated results indicate that the local structure of the (CrO6)9− cluster in TiO2:Cr3+ and MgO:Cr3+ systems exists as a compressed distortion relative to the regular octahedron. Meanwhile, the dependence of the EPR zero-field splitting parameter D on the local structure parameter ΔR (ΔR=R1−R2) has been revealed. In addition, the relation between the EPR g-factors (g,g,Δg) and the orbit reduction factor k has been discussed for the two systems, suggesting that the orbit reduction factor k is very important to understand the EPR g-factors. 相似文献