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91.
In the past, laser-induced breakdown spectroscopy (LIBS) signals have been reported to have a stability independent of the pulse length in solids. In this Letter, we perform the first stability study of femtosecond LIBS in gases (to our best knowledge) and show a significant improvement in signal stability over those achieved with longer pulses. Our study shows that ultrashort-pulse LIBS has an intrinsically higher stability in gas compared to nanosecond-pulse LIBS because of a deterministic ionization process at work in the femtosecond pulse. Relative standard deviations below 1% are demonstrated and are likely only limited by our laser output fluctuations. This enhanced emission stability may open up possibilities for a range of applications, from monitoring rapid gas dynamics to high-quality broadband light sources. 相似文献
92.
Xiaohe Liu Xianhui Wang Shiyu Zhen Guodong Sun Chunlei Pei Zhi-Jian Zhao Jinlong Gong 《Chemical science》2022,13(33):9537
PtCu single-atom alloys (SAAs) open an extensive prospect for heterogeneous catalysis. However, as the host of SAAs, Cu suffers from severe sintering at elevated temperature, resulting in poor stability of catalysts. This paper describes the suppression of the agglomeration of Cu nanoparticles under high temperature conditions using copper phyllosilicate (CuSiO3) as the support of PtCu SAAs. Based on quasi in situ XPS, in situ CO-DRIFTS, in situ Raman spectroscopy and in situ XRD, we demonstrated that the interfacial Cu+–O–Si formed upon reduction at 680 °C serves as the adhesive between Cu nanoparticles and the silicon dioxide matrix, strengthening the metal–support interaction. Consequently, the resistance to sintering of PtCu SAAs was improved, leading to high catalytic stability during propane dehydrogenation without sacrificing conversion and selectivity. The optimized PtCu SAA catalyst achieved more than 42% propane conversion and 93% propylene selectivity at 580 °C for at least 30 hours. It paves a way for the design and development of highly active supported single-atom alloy catalysts with excellent thermal stability.This paper describes PtCu single-atom alloys supported on copper phyllosilicate via Cu+–O–Si. The catalyst exhibits sintering resistance in propane dehydrogenation reaction without sacrificing activity and selectivity. 相似文献
93.
The friction at the liquid-solid interfaces is widely involved in various phenomena ranging from nanometer to micrometer scales. By the molecular dynamic(MD)simulation, the friction properties of liquid-solid interfaces at the molecular level are calculated via the Green-Kubo relation. It is found that the system size will influence the value of the friction coefficient, especially for the solid surfaces with the larger polar charge. The value of the friction coefficient decreases with the incre... 相似文献
94.
Yazhou Liu Tianjiao Shen Dr. Congcong Gao H. A. Abdulhadi El-Ali Na Gao Chunlei Yang Prof. Rubo Zhang Prof. Jing Jing Prof. Xiaoling Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(56):13017-13024
As some stimuli utilized in conventional drug delivery systems can also be found in normal cells, it is inevitable that encapsulated drugs escape from carriers into normal cells. Based on mutual interactions among proteins, polyphenol compounds, and metal ions, we developed a serial-stimuli-responsive drug delivery system. With multi-crosslinking structure, nanocapsules can maintain the integrity of the framework, even with a certain amount of stimuli present, and eventually reach tumor cells to initiate apoptosis, and protect normal cells from being damaged. Meanwhile, the fluorescence of DOX will be quenched when encapsulated in nanocapsules. This property means that the DOX that is released from nanocapsules can be monitored in real-time based on the recovery of fluorescence. These versatile nanocapsules exhibit great potentials to treat cancer. 相似文献
95.
Weisheng Hu Yaohui Jin Chun Jiang YUE Wang Xiaodong WANG Chunlei ZHANG Yang Lu Buwei Xu Peigang Hu Qingji Zeng 《光学学报》2003,23(Z1)
We build an automatically switched optical network (ASON) testbed with four optical cross-connect nodes. Many fundamental ASON features are demonstrated, which is implemented by control protocols based on generalized multi-protocol label switching (GMPLS) framework. 相似文献
96.
精确控制大数值孔径微透镜列阵面形的显影阈值方法 总被引:3,自引:1,他引:2
提出了一种可对大矢高、非球面微透镜阵列面形进行精确控制的新方法。针对不同面形的微透镜阵列,该方法首先对光致抗蚀剂表面的曝光分布进行设计,然后,利用光致抗蚀剂显影过程中的阈值特性,对微透镜的面形实行控制。当抗蚀剂显影速率接近0时,即可获得设计的微透镜面形。该方法不仅大大提高了微透镜阵列矢高的加工范围,而且还减小了光刻材料显影特性对微透镜面形的影响,提高了微透镜阵列的面形控制精度,在实验中获得了矢高达114μm的微透镜阵列。最终实现了大浮雕深度、大数值孔径、非球面微列阵光学元件的面形控制。 相似文献
97.
In this paper, we present a two-grid discretization scheme for semilinear parabolic integro-differential equations by $H^{1}$-Galerkin mixed finite element methods. We use the lowest order Raviart-Thomas mixed finite elements and continuous linear finite element for spatial discretization, and backward Euler scheme for temporal discretization. Firstly, a priori error estimates and some superclose properties are derived. Secondly, a two-grid scheme is presented and its convergence is discussed. In the proposed two-grid scheme, the solution of the nonlinear system on a fine grid is reduced to the solution of the nonlinear system on a much coarser grid and the solution of two symmetric and positive definite linear algebraic equations on the fine grid and the resulting solution still maintains optimal accuracy. Finally, a numerical experiment is implemented to verify theoretical results of the proposed scheme. The theoretical and numerical results show that the two-grid method achieves the same convergence property as the one-grid method with the choice $h=H^2$. 相似文献
98.
Liu Chunlei 《数学学报(英文版)》1996,12(2):141-150
In this paper it is proved that
相似文献
99.
采用柠檬酸法制备了SnO2纳米材料,并采用差热-热重、 X射线衍射、透射电子显微镜和氮吸附等技术对其进行了表征,考察了其在丙烯醛还原制烯丙醇反应中的催化性能. 结果显示,制备的SnO2纳米材料粒径(尺寸为8~10 nm)均一, 并具有多孔性质(孔径4~6 nm); 在丙烯醛还原制烯丙醇反应中具有良好的催化性能,催化剂的初始活性很高,丙烯醛的初始转化率可达93.6%, 烯丙醇的最高选择性为60%, 烯丙醇的最高收率为47%. 表面结焦是造成催化剂失活的主要原因. 相似文献
100.
Linbo Gong Shuling Gong Haiqing Dong Chunlei Zhang Yuanyin Chen 《Frontiers of Chemistry in China》2007,2(3):292-295
The reaction of 4′-hydroxy-4-methyl azobenzene (1) and 1,6-dibromohexane afforded 6-bromo-1-((4-((4-met hylphenyl)azo)phenyl)oxy)hexane (2), which further reacted with p-tert-butylcalix[4]arene to give the calix[4]arene derivative (3) whose lower rim had been modified by the azobenzene photochromic group. The structure of 3 was characterized by 1H-nuclear magnetic resonance (NMR) and electrospray ionization-mass spectrometry (ESI-MS). The fluorescence intensity of compound
3 was two to four times higher than that of compounds 1 and 2 as the azobenzene group concentration in the range of 1.6 × 10−5 to 8.0 × 10−4 mol/L, indicating that the fluorescence quantum yield of the azobenzene group had been improved through being attached to
the calix[4]arene skeleton. The liquid crystalline behavior of compound 3 was studied by polarized microscopy (POM) and differential scan calorimeter (DSC). Compound 3 exhibited the enchased texture of a smectic liquid crystal from 209.4°C to 219.5°C on heating, while 2 exhibited a liquid crystalline phase from 87.4 to 83.2°C on cooling. It was found that the calix[4]arene skeleton was a good
platform for conformation immobilization of azobenzene photochromic group and the formation of liquid crystalline.
Translated from Chinese Journal of Applied Chemistry, 2006, 23(9): 1023–1026 [译自: 应用化学] 相似文献
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