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991.
基于独特结构和物理特性的两类高性能新型高压半导体开关漂移阶跃恢复二极管和快速离化开关,提出一种新型高功率高压纳秒电磁脉冲产生方法,其技术路径是通过高压漂移阶跃恢复二极管开关将高贮能电感能量向高压快速离化开关及负载转移,产生高功率、高重复频率纳秒电磁脉冲,并用实验验证该方法在高重复频率(120,200,300 kHz)下产生高功率、高重复频率纳秒脉冲的有效性,输出脉冲电压分别为1.62,1.41,1.36 kV。 相似文献
992.
993.
极紫外(EUV)投影光刻掩模在斜入射光照明条件下,掩模成像图形位置和成像图形特征尺寸(CD)都将随入射光方向变化,即存在掩模阴影效应。基于一个EUV掩模衍射简化模型实现了掩模阴影效应的理论分析和补偿,得到了掩模(物方)最佳焦面位置和掩模图形尺寸校正量的计算公式。掩模(物方)焦面位置位于多层膜等效面上减小了图形位置偏移;基于理论公式对掩模图形尺寸进行校正,以目标CD为22 nm的线条图形为例,入射光方向变化时成像图形尺寸偏差小于0.3 nm,但当目标CD继续减小时理论公式误差增大,需进一步考虑掩模斜入射时整个成像光瞳内的能量损失和补偿。 相似文献
994.
《Journal of Coordination Chemistry》2012,65(12):2054-2064
Two iron(II) complexes, [FeII(pytBuN3)2](FeCl4) (1) and [FeII(pytBuMe2N3)Cl2] (2), with sterically constrained pytBuN3 and pytBuMe2N3 chelate ligands (pytBuN3 = 2,6-bis-(aldiimino)pyridyl; pytBuMe2N3 = 2,6-bis-(ketimino)pyridyl), have been synthesized and characterized by elemental analysis, IR, UV–vis spectra, and preliminary X-ray single-crystal diffraction. The latter revealed that Fe(II) in 1 is six-coordinate by six nitrogen donors from two bisiminopyridines in a distorted octahedron. Complex 2 reacts with thiourea with a second-order rate constant k2 = (2.50 ± 0.05) × 10?3 M?1 s?1 at 296 K, and the reaction seemed to be slow. In a similar way, the interaction of 2 and DNA was studied by fluorescence and absorption spectroscopy. The results revealed that 2 caused fluorescence quenching of DNA through a dynamic quenching procedure. The binding constants KA, Kapp, and KSV as well as the number of binding sites between 2 and DNA were determined. 相似文献
995.
Prof. Eric Collet Dr. Maciej Lorenc Dr. Marco Cammarata Dr. Laurent Guérin Dr. Marina Servol Dr. Antoine Tissot Dr. Marie‐Laure Boillot Prof. Hervé Cailleau Prof. Marylise Buron‐Le Cointe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(7):2051-2055
We study by 100 picosecond X‐ray diffraction the photo‐switching dynamics of single crystal of the orthorhombic polymorph of the spin‐crossover complex [(TPA)Fe(TCC)]PF6, in which TPA=tris(2‐pyridyl methyl)amine, TCC2?=3,4,5,6‐Cl4‐Catecholate2?. In the frame of the emerging field of dynamical structural science, this is made possible by using optical pump/X‐ray probe techniques, which allow following in real time structural reorganization at intra‐ and intermolecular levels associated with the change of spin state in the crystal. We use here the time structure of the synchrotron radiation generating 100 picosecond X‐ray pulses, coupled to 100 fs laser excitation. This study has revealed a rich variety of structural reorganizations, associated with the different steps of the dynamical process. Three consecutive regimes are evidenced in the time domain: 1) local molecular photo‐switching with structural reorganization at constant volume, 2) volume relaxation with inhomogeneous distribution of local temperatures, 3) homogenization of the crystal in the transient state 100 µs after laser excitation. These findings are fundamentally different from those of conventional diffraction studies of long‐lived photoinduced high spin states. The time‐resolution used here with picosecond X‐ray diffraction probes different physical quantities on their intrinsic time‐scale, shedding new light on the successive processes driving macroscopic switching in a functionalized material. These results pave the way for structural studies away from equilibrium and represent a first step toward femtosecond crystallography. 相似文献
996.
Effects of external electromagnetic fields on the conformational sampling of a short alanine peptide
Gleb Y. Solomentsev Niall J. English Damian A. Mooney 《Journal of computational chemistry》2012,33(9):917-923
Non‐equilibrium molecular dynamics simulations of a solvated 21‐residue polyalanine (A21) peptide, featuring a high propensity for helix formation, have been performed at 300 K and 1 bar in the presence of external electromagnetic (e/m) fields in the microwave region (2.45 GHz) and an r.m.s. electric field intensity range of 0.01–0.05 V/Å. To investigate how the field presence affects transitions between the conformational states of a protein, we report 16 independent 40 ns‐trajectories of A21 starting from both extended and fully folded states. We observe folding‐behavior of the peptide consistent with prior simulation and experimental studies. The peptide displays a natural tendency to form stable elements of secondary structure which are stabilized by tertiary interactions with proximate regions of the peptide. Consistent with our earlier work, the presence of external e/m fields disrupts this behavior, involving a mechanism of localized dipolar alignment which serves to enhance intra‐protein perturbations in hydrogen bonds (English, et al., J. Chem. Phys. 2010 , 133, 091105), leading to more frequent transitions between shorter‐lifetime states. © 2012 Wiley Periodicals, Inc. 相似文献
997.
K. J. de Almeida T. C. Ramalho M. C. Alves O. Vahtras 《International journal of quantum chemistry》2012,112(13):2571-2577
The density functional theory calculations were performed to investigate the specific solvent effects on the optical absorption spectrum of copper(II) hexafluoroacetylacetonate complex in pyridine. The effects of single and double coordination of pyridine molecules at axial position of bis(hexafluoroacetylacetonate) copper(II) indicate that both positions and intensities of 3d–3d electronic transitions are strongly dependent on the coordination environment around the copper(II) complex. The results indicate that the nature of the electron‐acceptor atoms in the equatorial ligands plays an important role in the number of solvent molecules in the first solvation shell of copper(II) acac systems. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
998.
999.
Analysis and finite element simulation of electromagnetic heating in the nitride MOCVD reactor 下载免费PDF全文
Electromagnetic field distribution in the vertical metal
organic chemical vapour deposition (MOCVD) reactor is simulated by
using the finite element method (FEM). The effects of alternating
current frequency, intensity, coil turn number and the distance
between the coil turns on the distribution of the Joule heat are
analysed separately, and their relations to the value of Joule heat
are also investigated. The temperature distribution on the
susceptor is also obtained. It is observed that the results of the
simulation are in good agreement with previous measurements. 相似文献
1000.
设计了一种基于电磁感应效应的转子扭转振动测量方法.该方法的思路是使线圈与永磁体做相对运动,根据线圈切割磁感应线的速度与感应电动势正相关的原理,由线圈两端的电压变化量计算各点的瞬时速度变化量,进而积分求出扭振信息.算法上采用半周期插值以及与标准信号进行对应点比较,保证了瞬时速度变化量的精确度.装置设计方面通过适当的空间布局,在一定程度上消除了轴向振动和部分横振的影响.实测验证表明,该方法得出了与输入载荷一致的扭振信息,具有精确性良好,安装简易,操作方便的特点. 相似文献