氟化氢泛频化学激光器高超音速低温喷管研究

通过建立一套氟化氢泛频化学激光器实验系统,介绍了一种新型高超音速低温喷管的结构及其实验参数设置方法;对喷管性能进行了测试,并将实验结果同数值模拟结果进行对比,找出了改善喷管性能的方法。由该喷管构成的激光系统已顺利出光。     

导体及其周围电离气体电磁俘获的数值模拟

介绍了圆柱导体周围稠密大气部分电离时导体对入射电磁场的散射特性的计算结果。采用了三维时域有限差分方法联合求解Maxwell方程组和空气离子方程组。结果表明,导体周围气体电离等离子体层的存在严重影响电磁场的散射特性,即电子等离子体与导体形成了谐振结构,在谐振频率上俘获了电磁场能量。     

The green synthesis of exceptional braided,helical carbon nanotubes and nanospiral platelets made directly from CO2

Helical carbon nanotubes currently cost ~15,000–19,000 USD/kg commercially and are ~10–15 times the price of straight carbon nanotubes of similar dimensions. They have not previously been made from the greenhouse gas CO₂ nor had new variants of the helical morphology been demonstrated. In this study, a novel, inexpensive electrosynthesis of these helical nanocarbon materials from CO₂ is presented. This material may be produced by molten carbon growth conditions that (1) maximize torsional stresses, such as those that may occur during rapid, nucleated carbon reduction, (2) enhance defects that cause formation of heptagonal, rather than the conventional hexagonal building blocks of graphene cylindrical walls, and (3) uniformly control those enhanced defects to repeatedly induce a uniform spiral conformation. These conditions are achieved with at least two of the following experimental conditions: (i) high electrolysis current density, (ii) sp³ defect-inducing agents, such as added oxide, and (iii) controlled concentration of iron added to the electrolyte or cathode. Here, it is shown with SEM, TEM, EDX, XRF, and Raman spectroscopy that a molten controlled electrolyte carbonate synthesis to induce defect formation, and a high rate of electrolysis (0.6 A/cm²) leads to a high yield of helical nanotubes, helical nanofibers, or helical nanoplatelet carbon morphologies.     

高功率TEA CO2激光器气体循环系统的设计

阐述了气体循环系统对高功率TEA CO2激光器的重要作用,分析了系统参数、结构组成及其设计。以体积流量法确定放电区气体流速,采用对称式的结构布局,选用轴流压气机和板翅式热交换器,加入系统附加阻力以确定风机静压参数。研究出的气体循环系统,放电区气体平均流速84.8 m/s,流速不均匀度纵向4.2%、横向0.38%;光学支架振动加速度4×10-2 m/s2,振动位移2.6×10-7 m。在放电体积2.5×10-3 m3、单脉冲注入能量276 J、放电脉宽150 ns条件下,实现了重复频率400 Hz均匀稳定的持续辉光放电,输出了高平均功率激光。     

1 MA直线型变压器驱动源模块设计

介绍了输出电流幅值为1 MA,电流上升时间为100 ns的快脉冲直线型变压器驱动源（LTD）模块的设计。模块由48个子块并联组成,每个子块由2个电容器和一个多级气体开关串联组成。48个开关由8路高压脉冲触发,每路高压脉冲（100 kV/50 ns）触发6个开关。电路模拟显示,在充电 90 kV条件下,输出电流幅值为1.04 MA,电流上升时间为84.5 ns（0~100%）和52 ns（10%~90%）。电路模拟时的参数设置以实验数据为基础,开关的工作条件与已研制成功的100 kA-LTD模块中的开关工作条件近似,模块设计工作于腔体注油状态以保证高压运行安全,能够保证模块达到设计要求。     

Effect of Negative Ion Generation on Complex Plasma Structure Properties

We propose a low-density discharge plasma model that takes into account the impact of oxygen admixture in typical conditions of complex (dusty) plasmas. Numerical simulations based on this model show that the concentration of negative ions turns out to be very high, and they play an important role in the overall kinetics in this particular range of plasma conditions. The ambipolar diffusion electric field drags these negative ions into the center of the plasma. The density of negative ions is high enough to push the negatively charged dust component out of the center, both by weakening the radial electric field and by increasing the thermophoretic force. This phenomenon was observed in the published experiment and qualitatively supports the proposed model. Additionally, the proposed model allows an alternative explanation of the experiment.     

陡化前沿Marx发生器的设计与初步实验

设计了10级同轴结构的陡化前沿Marx发生器,实现了电容储能型脉冲功率调制系统的小型化。该系统采用3 nF低电感电容器作为储能电容,采用固体电阻作为充电电阻,通过各级短间隙气体火花开关迅速放电及级间紫外光耦合在50 Ω负载上建立了陡化前沿的输出电压波形。在考虑开关电极分散电容、等效传输线效应及回路电感等因素基础上,利用自击穿火花开关模型建立了等效放电电路模型,并利用PSpice电路模拟软件进行了数值模拟。根据数值模拟结果设计加工了10级陡化前沿的Marx发生器实验装置,在较低充电电压下（7 kV与11 kV）,得到了初步实验结果,输出电压波形大致为方波,相对于传统Marx发生器输出前沿缓慢的三角波有较大改善,半高宽为40~50 ns,前沿时间为十几ns,幅值约为41 kV和57.5 kV,实验结果与模拟结果基本一致。     

Scalable Synthesis of Robust MOF for Challenging Ethylene Purification and Propylene Recovery with Record Productivity

Ethylene (C₂H₄) purification and propylene (C₃H₆) recovery are highly relevant in polymer synthesis, yet developing physisorbents for these industrial separation faces the challenges of merging easy scalability, economic feasibility, high moisture stability with great separation efficiency. Herein, we reported a robust and scalable MOF (MAC-4) for simultaneous recovery of C₃H₆ and C₂H₄. Through creating nonpolar pores decorated by accessible N/O sites, MAC-4 displays top-tier uptakes and selectivities for C₂H₆ and C₃H₆ over C₂H₄ at ambient conditions. Molecular modelling combined with infrared spectroscopy revealed that C₂H₆ and C₃H₆ molecules were trapped in the framework with stronger contacts relative to C₂H₄. Breakthrough experiments demonstrated exceptional separation performance for binary C₂H₆/C₂H₄ and C₃H₆/C₂H₄ as well as ternary C₃H₆/C₂H₆/C₂H₄ mixtures, simultaneously affording record productivities of 27.4 and 36.2 L kg⁻¹ for high-purity C₂H₄ (≥99.9 %) and C₃H₆ (≥99.5 %). MAC-4 was facilely prepared at deckgram-scale under reflux condition within 3 hours, making it as a smart MOF to address challenging gas separations.     

Dimethyl Carbonate Synthesis from CO2 over CeO2 with Electron-Enriched Lattice Oxygen Species

Direct synthesis of dimethyl carbonate (DMC) from CO₂ plays an important role in carbon neutrality, but its efficiency is still far from the practical application, due to the limited understanding of the reaction mechanism and rational design of efficient catalyst. Herein, abundant electron-enriched lattice oxygen species were introduced into CeO₂ catalyst by constructing the point defects and crystal-terminated phases in the crystal reconstruction process. Benefitting from the acid-base properties modulated by the electron-enriched lattice oxygen, the optimized CeO₂ catalyst exhibited a much higher DMC yield of 22.2 mmol g^-1 than the reported metal-oxide-based catalysts at the similar conditions. Mechanistic investigations illustrated that the electron-enriched lattice oxygen can provide abundant sites for CO₂ adsorption and activation, and was advantageous of the formation of the weakly adsorbed active methoxy species. These were facilitating to the coupling of methoxy and CO₂ for the key *CH₃OCOO intermediate formation. More importantly, the weakened adsorption of *CH₃OCOO on the electron-enriched lattice oxygen can switch the rate-determining-step (RDS) of DMC synthesis from *CH₃OCOO formation to *CH₃OCOO dissociation, and lower the corresponding activation barriers, thus giving rise to a high performance. This work provides insights into the underlying reaction mechanism for DMC synthesis from CO₂ and methanol and the design of highly efficient catalysts.     

Response surface methodology optimization of extraction and enrichment conditions of total triterpenoid saponins from Celosiae Semen and evaluation of its lipid-lowering activity

The saponin-enriched extract from Celosiae Semen is a promising resource owing to its lipid-lowering activity. However, triterpenoid saponins are difficult to extract owing to their high molecular weight and strong water solubility. The aim of this paper was to explore an eco-friendly and effective technology of extraction and enrichment of total triterpenoid saponins to obtain high lipid-lowering fractions. Initially, Box–Behnken design experiments were employed to optimize the heat reflux extraction process on the basic of mono-factor experiments. Afterwards, the crude extract was further purified using D-101 resin, and the purification parameters were investigated based on adsorption/desorption experiments and biological activity assay. Under optimal conditions, the purity of the finally obtained total triterpenoid saponins was increased by 7.28-fold. The lipid-lowering activities of the six main triterpenoid saponins were evaluated in HepG2 cells induced by palmitic acid. The results of Oil Red O staining showed that the compounds all exhibited potential lipid-lowering activity. The structure–activity relationship analysis suggested that the oligosaccharide chain at C-28 played an essential role in their lipid-lowering activity and the substituent group at C-23 site also showed important effects. The optimal extraction and purification methods may facilitate the utilization of Celosiae Semen for the industrial production as a functional food and drug.