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SYNOPSISThe kinetics of graft copolymerization of polyacrylonitrile (PAN) onto polyester (PET) and the simultaneous homopolymerization initiated by the potassium penoxomonosulfate (PMS)-ascorbic acid (H,A) redox system were studied separately. Results on the graft copolymerization was adequately explained by a mechanism which also accounts for the reason for simultaneous homopolymerization. The observed homopolymerization results agreed with the proposal. Kinetic chain-length measurements on the graft copolymer and homopolymerization were used to evaluate the kinetic parameters. 0 1995

SYNOPSISThe kinetics of graft copolymerization of polyacrylonitrile (PAN) onto nylon 6/nylon 66 and the simultaneous homopolymerization initiated by potassium peroxornonosulfate (PMS)-ascorbic acid ( H2A) redox systems were studied separately. Various kinetics parameters were evaluated and analyzed to have a comparison among the systems. The occurrence of simultaneous homopolymerization was evident through rate parameters. When the backbone was changed, the following order was observed for grafting efficiency: polyester (PET) > nylon 6 k nylon 6 6 . 0 1995 John Wiley & Sons, Inc. I NTRO DUCT10 NGraft copolymerization onto nylon appears to be a very fascinating field for research with unlimited future possibilities for improving its properties. For example, nylon grafted with styrene is insoluble in formic acid, phenol, and rn-cresol and showed a good water repellency when more than 10% is grafted on.' On the other hand, it has been reported that when nylon is grafted with acrylic, methacrylic, and maleic acids, the water absorbency, heat resistance, and antistatic properties are Considerable enhancement of the wet crease recovery is noticed when nylon is grafted with acrylamide, divinylsulfones, and Nvinylpyrrolidine. The dyeability of nylon is improved when grafting is carried out with the last named m~n o m e r .~,~ Graft copolymerization of vinyl polymers onto substrate polymers is generally considered to involve the generation of reactive sites on the polymer in a conventional manner. This can be achieved by several means such as high-energy ra-

This paper focuses its attention on extractive summarization using popular graph based approaches. Graph based methods can be broadly classified into two categories: non-PageRank type and PageRank type methods. Of the methods already proposed-the Centrality Degree method belongs to the former category while LexRank and Continuous LexRank methods belong to later category. The paper goes on to suggest two enhancements to both PageRank type and non-PageRank type methods. The first modification is that of recursively discounting the selected sentences, i.e. if a sentence is selected it is removed from further consideration and the next sentence is selected based upon the contributions of the remaining sentences only. Next the paper suggests a method of incorporating position weight to these schemes. Thus we have experimented with 12 methods-six of non-PageRank type and six of PageRank type. To clearly distinguish between various schemes, we call the methods of incorporating discounting and position weight enhancements over Lexical Rank schemes as Sentence Rank (SR) methods. Intrinsic evaluation of all the 12 graph based methods were done using conventional Precision metric and metrics earlier proposed by us-Effectiveness1 (E1) and Effectiveness2 (E2). Experimental study brings out that the proposed SR methods are superior to all the other methods.

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