西洋参皂甙的核磁共振波谱研究——Ⅰ.西洋参叶中 Ocotillol型皂甙的结构分析

本文用常规一维~1H、~(13)C核磁共振波谱和远程异核化学位移相关谱。异核化学位移相关谱和同核化学位移相关谱技术研究了西洋参叶中首次分离出的一种Ocotillol型皂甙,确认了化学结构,并对其~(13)C、~1H NMR谱线进行了归属。     

含氟离聚体的多相结构及大分子链运动的NMR研究

本文用~(13)C自旋-自旋弛豫时间T_2表征了以丙烯酸-1,1,5-三氢全氟戊酯-丙烯酸共聚物为基础的离聚体体系的多相结构和大分子链段运动特性,结果表明:离子微区和聚合物基体之间存在界面层,聚合物主链的运动活性与离聚体的共聚物组成、金属离子特性、离子化程度、离子微区的稳定性和离子微区内的精细结构均有密切关系.     

Synthesis of copolymers of N-vinylpyrrolidone and 2-ethylhexyl acrylate by DL-methionine-mediated reversible deactivation radical polymerization and their dispersion behavior in preparation of LiFePO4 battery positive slurry with high solid content

Dispersants play a significant role in the formulation of positive battery slurry. Adding a small amount of dispersant can effectively reduce the viscosity of the slurry, which is beneficial for the production of positive batteries. A series of copolymers of N-vinylpyrrolidone (NVP) and 2-ethylhexyl acrylate (2-EHA) with different molar ratios of NVP to 2-EHA, different polymer molecular weights and different polymer structures are synthesized by dl -methionine-mediated reversible deactivation radical polymerization. The ability of these copolymers to disperse LiFePO₄ battery positive slurry with a high solid content (57.08%) as dispersants has been evaluated. Research shows that when the ratio of NVP to 2-EHA is 20 and the polymer molecular weight is 6000, poly(N-vinylpyrrolidone-ran-2-ethylhexyl acrylate) (NVP-ran-2-EHA) exhibits the strongest dispersing ability to the slurry. This polymer can reduce the viscosity of the slurry by 43.925% and has the longest stabilization time of 3 h, which is better than poly(N-vinylpyrrolidone) (PVP) and poly(N-vinylpyrrolidone)-block-poly(2-ethylhexyl acrylate) (PVP-b-PEHA) with the same molecular weight.     

Influence of ground granulated blast furnace slag on the early hydration and microstructure of alkali-activated converter steel slag binder

Journal of Thermal Analysis and Calorimetry - Alkali-activated materials are low-environmental-impact binders that can be obtained from the alkaline activation of industrial wastes. In this study,...     

有源消声耳罩的研究

本文提出一种把闭环反馈式控制方式和开环前馈式控制方式结合在一起的复合式消声耳罩,并给出了原理式和具体的结构。理论和实验表明这种复合式结构具有有源消声频带宽、消声效果好的特点。     

Activated carbon from the waste water purifier for supercapacitor application

Journal of Solid State Electrochemistry - Activated carbon has been synthesized from the waste filter carbon in household water purifier. The original waste filter carbon (OFC) gives poor specific...     

Radical‐induced oxidation of RAFT agents—A kinetic study

Radical‐induced oxidation of reversible addition‐fragmentation chain transfer (RAFT) agents is investigated with respect to the effect of molecular structure on oxidation rate. The radicals are generated by homolysis of either azobisisobutyronitrile or alkoxyamine and transformed in situ immediately into peroxy radicals through transfer to molecular oxygen. It is found that the oxidation rate depends on the structure of Z‐ and R‐group of thiocarbonylthio compounds. For dithioesters with identical Z‐phenyl substituent, the oxidation rate decreases in the order of cyanoisopropyl (? C(Me)₂CN) > cumyl (? C(Me)₂Ph) > phenylethyl (? CH(Me)Ph) > 2‐methoxy‐1‐methyl‐2‐oxoethyl (? CH(Me) ? C(?O)OCH₃) > benzyl (? CH₂Ph). For dithioesters with identical R‐group, the oxidation rate decreases in the order of Z = phenyl? ～ benzyl? > RS? (trithiocarbonates) > RO? (xanthates). The stability of the RAFT agents toward oxidation correlates well with the chain transfer abilities as those previously reported by Rizzardo and coworkers. The priority of the oxidation reaction over the RAFT process, and the subsequent influence on RAFT polymerization are also investigated. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

有源消声耳罩控制器的实现

本文用传递函数描述了复合式有源消声耳罩的系统模型,确定了模拟式消声控制器的合理阶次,对于前馈控制器和反馈控制器,均比出了电路实现方案,最后,实际设计了复合式有源消声耳罩,并实测了控制器特性和消声效果,验证了本文提出了的控制器实现方法的有效性。     

Rapid synthesis of kahweofuran and its derivatives, the coffee aroma components

Kahweofuran, as an impact flavor component of roasted coffee and possesses the 6-methyl-2,3-dihydrothieno[2,3-c]furan structure, was rapidly synthesized from 2-acetyl-3-hydroxymethylthiophene by the formal reductive cyclization using the Wilkinson’s catalyst. Similarly, the syntheses of the 4-methyl, 6-ethyl and 4,6-dimethyl derivatives were also achieved in favorable yields.     

高阻抗伏特计的设计

阐述自制高阻抗伏特计的电路设计原理与组装技术。