PREPARATION OF POLYETHERSULFONE ULTRAFILTRATION MEMBRANES FOR MILK CONCENTRATION AND EFFECTS OF ADDITIVES ON THEIR MORPHOLOGY AND PERFORMANCE

Polyethersulfone membranes were prepared from quaternary systems containing N,N-dimethylacetamide （DMAc） as solvent, polyvinylpyrrolidone （PVP） as constant additive and acetic acid, acetone and water as variable additives. Phase inversion via immersion precipitation was employed for manufacturing of membranes. The prepared films were immersed in the mixture of pure water and 2-propanol （30/70 vol%） as the non-solvent. Acetic acid caused an increment in the flux at high polymer concentration （16 wt%） and a decline in the flux at low polymer concentrations （10 wt% and 13 wt%）. Acetone and water as the solvent in the casting solution declined the flux at any polymer concentration tested. The morphology and performance of the prepared membranes were investigated by scanning electron microscopy and separation experiments using milk as the feed.     

INFLUENCE OF MOLECULAR STRUCTURES OF SECONDARY AMINE TERMINATED POLY（ESTER-AMINE）S ON THE CURING PERFORMANCE WITH EPOXY RESIN

Five secondary amine terminated poly(ester-amine)s(defined as PEA)with controlled molecular structures were synthesized through reacting excessive piperazine with phthalicdiglycol diacrylate(PDDA)and 1,1,1-trimethylolpropane triacrylate(TMPTA)at a constant secondary amine/acrylate group ratio of 1.5/1 and at different PDDA/TMPTA molar ratios. Both IR and ~(?)H-NMR spectra indicated that all acrylate groups were consumed in the reaction,based on which the structural parameters were calculated from the ~(?)H-NMR spectra.With decreasing PDDA/TMPTA ratio,the content of secondary amine,degree of branching,molecular weight,T_g and T_d increased accordingly.These polymers were further used as both crosslinkers and flexibilizers for a linear epoxy resin E51 to form cured films under ambient condition.The gel content, relative hardness and T_g of the resulting films increased as PEA molecules changed from linear to highly branching structures.Due to the flexibility of PEA molecules,all the films possessed excellent mechanical performance.     

卟啉化合物的热化学研究: V. 含溴卟啉化合物的标准燃烧能和生成焓

用本实验室建立的精密转动氧弹燃烧热量计测定了标准物质对溴苯甲酸、辅助物质鲨烷及四对溴苯基卟啉(Tp-BrPP)的标准燃烧能, 并计算出了它们的标准生成焓。     

云团中顺磁性粒子对三重态正电子素寿命的影响

Ferrell很早就提出了正电子素o-Ps的猝灭理论,指出介质中的顺磁性粒子是影响o-Ps寿命的重要因素.Lee等测出O_2猝灭o-Ps的速率常数为10~(10)～10~(11)mol·L~(-1)·s~(-1),得出了顺磁猝灭反应是扩散控制的结论.但前人没有对云团中瞬态活性粒子对o-Ps的影响加以探讨.本文通过o-Ps寿命与氧分压的关系来研究云团中瞬态活性粒子对o-Ps猝灭的影响.     

GENERALIZATION PERFORMANCE OF MULTI-CATEGORY KERNEL MACHINES -In Memory of Professor Sun Yongsheng

Support vector machines are originally designed for binary classification. How to effectively extend it for multi-class classification is still an on-going research issue. In this paper, we consider kernel machines which are natural extensions of multi-category support vector machines originally proposed by Crammer and Singer. Based on the algorithm stability, we obtain the generalization error bounds for the kernel machines proposed in the paper.