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排序方式: 共有418条查询结果,搜索用时 31 毫秒
1.
HIRFL–CSR加速器中束流与真空中剩余气体的碰撞损失 总被引:1,自引:1,他引:0
研究了重离子加速器中束流与真空中剩余气体的碰撞损失过程和碰撞截面,在依据大量实验数据的基础上,提出了一组计算离子一原子的电荷交换截面的经验公式.以兰州重离子加速器HDRFL及冷却储存环CSR为例,给出了依据碰撞截面的公式计算束流在加速器真空中的传输效率的方法,并计算了在不同真空度下HIRFL的ECR源轴向注入束运线、注入器SFC、前束运线、主加速器SSC和后束运线等不同加速阶段及CSR的传输效率,并提出合理的真空度要求.HIRFL的真空分布测量和束流的损失测量证明了该计算方法的可靠性. 相似文献
2.
Cluster ions have been recognized as a superb primary species in time of flight secondary ion mass spectroscopy (ToF-SIMS) compared with monatomic primary ions, as they significantly enhance the secondary ion yields from bulk samples. Self-assembled monolayers provide an important system for studying the fundamental mechanism involved in the yield enhancement.We used a gold cluster ion source to analyze a new type of self-assembled monolayer: a fluorocarbon-grafted polyethylene terephthalate. In addition to the structure details, which helped to understand the grafting mechanism, ToF-SIMS analysis revealed that fluorocarbon secondary ion yield enhancements by cluster ions were due to the enhanced sputter efficiency. A larger information depth may also be expected from the enhancement. Both mathematical definitions of damage cross-section and disappearance cross-section were revisited under a new context. Another cross-section parameter, sputter cross-section, was introduced to differentiate the beam induced sputter process from damage process. 相似文献
3.
This paper deals with the asymptotic analysis of the three-dimensional problem for a linearly elastic cantilever having an
open cross-section which is the union of rectangles with sides of order ε and ε
2, as ε goes to zero. Under suitable assumptions on the given loads and for homogeneous and isotropic material, we show that the
three-dimensional problem Γ-converges to the classical one-dimensional Vlassov model for thin-walled beams.
相似文献
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5.
A. S. Yasyukevich V. G. Shcherbitskii V. É. Kisel' A. V. Mandrik N. V. Kuleshov 《Journal of Applied Spectroscopy》2004,71(2):202-208
A new method of determining the stimulated emission cross-section spectra from the absorption cross-section spectra, which we call the integral method of reciprocity, is suggested it does not require knowledge of the structure of the impurity-center electron levels. Based on this method, formulas for calculating the radiation lifetime of impurity centers in crystals have been derived. The effectiveness of the integral method of reciprocity was demonstrated in determining the stimulated emission cross sections and radiation lifetime of an ytterbium ion in the laser crystals Yb3+:KYW and Yb3+:KGW. 相似文献
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7.
Thomas Wloka Prof. Dr. Michael Gottschaldt Prof. Dr. Ulrich S. Schubert 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(32):e202104191
Two-photon polymerization (2PP) represents a powerful technique for the fabrication of precise three-dimensional structures on a micro- and nanometer scale for various applications. While many review articles are focusing on the used polymeric materials and their application in 2PP, in this review the class of two-photon photo initiators (2PI) used for radical polymerization is discussed in detail. Because the demand for highly efficient 2PI has increased in the last decades, different approaches in designing new efficient 2PIs occurred. This review summarizes the 2PIs known in literature and discusses their absorption behavior under one- and two-photon absorption (2PA) conditions, their two-photon cross sections (σTPA) as well as their efficiency under 2PP conditions. Here, the photo initiators are grouped depending on their chromophore system (D-π-A-π-D, D-π-D, etc.). Their polymerization efficiencies are evaluated by fabrication windows (FW) depending on different laser intensities and writing speeds. 相似文献
8.
考虑爆炸成型弹丸(explosively-formed projectile,EFP)变截面的特性,基于流体力学Bernoulli方程和绝热剪切理论,改进了EFP垂直侵彻装甲钢板靶后破片质量模型,结合已有的试验数据和数值仿真方法检验了改进后模型的准确性。在此基础上,分析了靶板厚度和EFP着靶速度对靶板和EFP产生的靶后破片质量的影响规律。结果表明:相比于改进前的模型,改进后的模型能够更准确地解释靶板和EFP产生的靶后破片质量随靶板厚度和EFP着靶速度的变化规律;当EFP着靶速度为1 650 m/s时,随着靶板厚度从30 mm增大到70 mm,EFP变截面的特性对靶板和EFP产生靶后破片质量的影响不断增强;当靶板厚度为40 mm时,随着EFP着靶速度从1 650 m/s升高到1 860 m/s,EFP变截面的特性对靶板和EFP产生靶后破片质量的影响不断减弱。 相似文献
9.
MA En CHEN Da-Qin HU Zhong-Jian LIU Feng HUANG Zi-Xiang BAO Feng WANG Yuan-Sheng ② 《结构化学》2007,26(3):303-308
The distribution characteristics of Er3+ ions doped in the oxyfluoride glass ceramics containing LaF3 nanocrystals heat-treated at 650 ℃ for different durations were investigated. The results of the integral absorption cross-section analysis demonstrated that the partition fraction of Er3+ in LaF3 nanocrystals increases with prolonging of heating time. The anomalous phenomena of Er3+ emissions in the up-and the down-conversion fluorescence spectra are well explained based on the calculated results. 相似文献
10.
PeiDe Zhao Ping Chen GuoQing Tang JinWei Liu Lie Lin Peng Guo Qing Yu JianZhong Yao DongMing Ma GuiLan Zhang WenJu Chen 《中国科学B辑(英文版)》2008,51(6):529-538
The spectroscopic properties of a new chlorophyll derivate photosensitizer(CDP) are studied under the excitation wavelengths at 800 and 400 nm using femtosecond pulses from a Ti:sapphire laser.The damaging effect of CDP on the BEL-7402 cancer cells is also investigated upon two-photon illumination at 800 nm.The normalized fluorescence spectra of CDP in tetrahydrofuran(THF) show that two-photon and one-photon spectra have the same distributions and the same emission bands(675 nm).The life-times of two-and one-photon induced fluorescence of this molecule are of the order of 5.0 ns.By comparing the data it is shown that there is some difference between the two lifetimes,but the differ-ence is less than one nanosecond.The two-photon absorption cross section of the molecule is also measured at 800 nm and estimated as about σ′2 ≈ 31.5×10-50 cm4·s·photon-1.The results of two-photon photodynamic therapy(TPPDT) tests show that CDP can kill all of the tested cancer cells according to the usual Eosine assessment.Our results indicate that the two-photon-induced photophysical,photo-chemical and photosensitizing processes of CDP may be basically similar to those of one-photon ex-citation.These behaviors of the sample suggest that one may find other possible methods to estimate some photosensitizers' effects in details such as their distribution in cells and the reactive targets of the sub-cellular parts of some tumor cells via two-photon excitation techniques. 相似文献