叶片锯齿尾缘对降低空调室外机气动噪声影响的试验研究

依据现有的叶片尾迹宽度计算公式,计算了一空调室外机风机叶片的尾迹宽度,然后,以此尾迹宽度为参考基准,设计了两组不同形状和大小的锯齿形叶片尾缘,制作并试验研究了锯齿形尾缘对风机气动噪声的影响规律。结果表明,锯齿尾缘有明显降噪效果,正弦形锯齿较正三角形更好。锯齿尾缘通过降低宽频噪声降噪,而对离散噪声影响很小。采用与叶片尾迹...     

Klein–Nishina Effect and the Cosmic Ray Electron Spectrum

Radiative energy losses are very important in regulating the cosmic ray electron and/or positron(CRE) spectrum during their propagation in the Milky Way. Particularly, the Klein–Nishina(KN) effect of the inverse Compton scattering(ICS) results in less efficient energy losses of high-energy electrons, which is expected to leave imprints on the propagated electron spectrum. It has been proposed that the hardening of CRE spectra around 50 GeV observed by Fermi-LAT, AMS-02, and DAMPE could be due to the KN effect. We show in this work that the transition from the Thomson regime to the KN regime of the ICS is actually quite smooth compared with the approximate treatment adopted in some previous works. As a result, the observed spectral hardening of CREs cannot be explained by the KN effect. It means that an additional hardening of the primary electrons spectrum is needed. We also provide a parameterized form for the accurate calculation of the ICS energy-loss rate in a wide energy range.     

The behavior of technetium in technetium-scrubbing stage of PUREX process

Technetium decontamination factor as a function of the acidity, flow ratio, scrubbing stage number was investigated by counter-current cascade experiments or mixer-settler batch tests. Results showed that the acidity of the scrubbing acid has little influence on the decontamination factor of technetium when the acidity was kept in the range of 4.5–6 M. The most effective method to increase the decontamination factor is to lower the feed-to-acid flow ratio. Keeping other condition same the factor increased to 10.3 from 3.1 when feed-to-acid ratio changed to 4 from 5.6. The loss of uranium and plutonium can be recovered through a re-extraction technology.     

Electrochemical performance of a nonaqueous rechargeable lithium-air battery

Nonaqueous rechargeable lithium-air battery has so high specific capacity and specific energy that it is being widely researched by academia, corporation, and different research institutes. When used in dried air and absorbing oxygen form the air, this battery is called lithium-air battery, and its specific capacity based on cathode active material (oxygen) is infinite. However, its cycle performance is very limited as reported by the state-of-the-art researches. This cycle problem is mainly caused by instability of electrolyte. Based on electroanalysis of materials’ electrochemical property, a stable electrolyte solvent (sulfolane) and a lithium salt LiBF₄ are selected as electrolytes in this work. Coupled with other eligible battery materials and careful assembly, the lithium-air battery exhibits favorable cycle performance. Above all, this lithium-air system is evaluated objectively in this paper.     

Synthesis, Structure and H+/K+-ATPase Inhibitory Activity of Novel Triazolyl Substituted Tetrahydrobenzofuran Derivatives via One-pot Three-component Click Reaction

Eleven triazolyl substituted tetrahydrobenzofuran derivatives were synthesized in high yields as novel H⁺/K⁺‐ATPase inhibitor via one‐pot CuI‐catalyzed three‐component click reaction of azide, secondary amine and 3‐bromopropyne under mild conditions in water. Their structures were characterized by NMR, IR, ESI‐MS, elemental analysis and single‐crystal X‐ray diffraction analysis. Most of the target compounds exhibited better H⁺/K⁺‐ATPase inhibitory activity than commercial omeprazole with IC₅₀ values less than 15 µmol·L^?1. The initial structure‐activity analysis suggested that the triazole substituted by cycloalkyl, aromatic ring or O‐containing side‐chain seemed to be beneficial for enhancing the activity.     

Cross-flow heat transfer in fixed bed

Radial flow reactor operated at cross-flow heat transfer is focused for large scale methanol synthesis. The effects of operating conditions including the reactor inlet air temperature, the heating pipe temperature and the air flow rate on the cross-flow heat transfer were investigated and results show that the temperature profile of the area in front of the heating pipe is slightly affected by all the operating conditions. The main area whose temperature profile is influenced is located behind the heating pipe. The heat transfer direction is related to the direction of the flow. In order to obtain the basic parameters for radial flow reactor designing calculation, the dimensionless number group method was used for data fitting of the bed effective thermal conductivity and the wall heat transfer coefficient which were calculated by the mathematical model with the product of Reynolds number and Prandtl number. The comparison of experimental data and calculated values shows that the calculated values fit the experimental data satisfactorily and the formulas can be used for reactor designing calculation.     

高电荷态离子207Pbq+(24≤q≤36)与Si(110)固体表面作用的电子发射研究

报道了利用兰州重离子加速器国家实验室ECR源引出的高电荷态离子²⁰⁷Pb^q+(24≤q≤36)入射到Si(110)表面产生的电子发射的实验测量结果.结果表明,高电荷态离子与固体表面相互作用产生的电子发射产额Y与入射离子的电荷态q、入射角度ψ和入射能量E都有很强的关联.首次发现,电子发射产额Y与入射角度ψ间有接近1/tanψ的关系.理论分析认为,这些过程与基于经典过垒模型的势能电子发射过程密切相关. 关键词： 高电荷态离子 经典过垒模型 电子发射产额     

Coupled intramolecular/heterointerfacial electron transfer in polyelectrolyte-shielded Iso-type black phosphorus hetero-structure boosts oxygen reduction kinetics

Searching new structured black phosphorus (BP) and exploring intriguing functions and applications have become a hot topic so far.Here,we introduce a novel Iso-...     

LiAl5O8高压相变研究

 运用金刚石压砧同步辐射X射线衍射,对尖晶石结构的LiAl₅O₈进行了高压原位研究。实验发现：在高压下,一组LiAl₅O₈的新相衍射峰出现,随着压力的增加,其新相衍射峰逐渐增强,当压力增加到45.0 GPa时,LiAl₅O₈的低压相衍射峰全部消失,而形成了一组高压新相衍射峰。采用指标化程序对衍射数据进行处理和分析,确定这一高压新相为正交晶系结构,其晶胞参数为a=0.995 9 nm,b=0.644 7 nm,c=0.333 4 nm ,空间群为Pmm2。     

Effect of heat treatment on electronic phase in underdoped La2-xSrxCuO4 single crystal

Superconducting La1.937Sr0.063CuO4 crystals grown by the travelling-solvent floating-zone technique were thermally treated under various temperatures and oxygen pressures for moderately adjusting the oxygen content. The response of intrinsic electronic property of the crystals to the change of hole density in La2-xSrxCuO4 in the vicinity of the magic doping of x= 1/16 （= 0.0625） is studied in detail by magnetic measurements under various fields up to 1 T. It is found that when the superconducting critical temperature （Tc） increases with the oxygen content, there appears also a new subtle electronic state that can be detected from the differential curves of diamagnetic susceptibility dx/dT of the crystal sample. In contrast with the intrinsic state, the new subtle electronic state is very fragile under the magnetic fields. Our results indicate that a moderate change in oxygen doping does not significantly modify the intrinsic electronic state originally existing at the magic doping level.