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本文引入时间变量来分析制度变迁的经济绩效,认为在不同的时间跨度内,制度变迁的经济绩效传导途径有所不同。短期内,制度创新通过降低交易费用,从而直接提高生产效率和实现经济增长;长期内,制度从属于技术创新的要求,其绩效通过对技术创新的作用而间接地体现出来;从短期和长期来看,制度变迁绩效都呈递减趋势,但两者成因完全不同。

关键词：制度变迁经济绩效绩效曲线

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An oblivious fragile watermarking scheme for images utilizing edge transitions in BTC bitmaps

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Science china(Information Sciences) 2012年第11期55卷 2570-2581页

作者： ZHANG Yong1,LU ZheMing2 & ZHAO DongNing1 1ATr National Defense Technology Key Laboratory,College of Information Engineering,shenzhen univ.rsity,shenzhen 518060,{4. 2School of Aeronautics and Astronautics,Zhejiang univ.rsity,Hangzhou 310027,{4. 1. ATr National Defense Technology Key Laboratory College of Information Engineering Shenzhen University Shenzhen 518060 China2. School of Aeronautics and Astronautics Zhejiang University Hangzhou 310027 China

As one of the famous block-based image coding schemes,block truncation coding(BTC) has been also applied in digital *** BTC-based watermarking or hiding schemes usually embed secret data by modifying the BTC encoding stage or BTC-compressed data,obtaining the watermarked image with poorer quality than the BTC-compressed *** pap.r.presents a new oblivious image watermarking scheme by exploiting BTC *** the traditional schemes,our ap.r.ach does not really p.r.orm the BTC compression on images during the embedding process but utilizes the p.r.ty of the number of horizontal edge transitions in each BTC bitmap to guide the watermark embedding and extraction *** embedding process starts by p.r.itioning the original cover image into non-overlapping 4.4.blocks and p.r.orming BTC on each block to obtain its BTC *** watermark bit is embedded in each block by modifying at most three pixel values in the block to make sure that the p.r.ty of the number of horizontal edge transitions in the bitmap of the modified block is equal to the embedded watermark *** the extraction stage,the suspicious image is first p.r.itioned into non-overlapping 4.4.blocks and BTC is p.r.ormed on each block to obtain its ***,by checking the p.r.ty of the number of horizontal edge transitions in the bitmap,we can extract one watermark bit in each *** results demonstrate that the proposed watermarking scheme is fragile to various image processing op.r.tions while keeping the transp.r.ncy very well.