Robustness of Watermarking:Is Error Correcting Coding Effective?

Robustness is one of the most important requirements of digital watermarking for many applications.Spread-spectrum based methods are not effective enough to ensure their robustness.By modeling digital watermarking as digital communications,several researchers proposed using error correcting coding(ECC)to improve robustness.However,an important fact that has long been neglected is that due to the imperceptibility requirement,the redundancy introduced by ECC will lead to a decrease of the magnitude of watermark signal.Therefore,a problem arises naturally: Could the usage of ECC effectively improve the robustness of watermarking?This paper addresses this problem from the perspectives of both theoretical analysis and experimental investigation.Our investigation shows that ECC cannot effectively improve the robustness of watermarking against a great majority of various attacks except for cropping and jitter attacks.Hence,ECC should not be considered as a universal measure that can be employed to enhance robustness of watermarking.     

遮住黑暗中窥视的眼睛——当心Foxmail的加密密码被还原

笔者最常用的邮件客户端软件是Foxmail5．0，相信许多人也在用它，因为它的界面简洁、功能强大。在使用Foxmail的过程中发现一个问题，即Foxmail邮箱密码不够安全!而且这个问题在Foxmail4．x和5．0正式版(包括测试版)中都存在，在这里提醒大家注意保管好自己的密码。     

ANALYSIS OF STRESS AND TEMPERATURE IN THE CONFORM FORMING PROCESS——FOUNDATION THEORY

ＡＮＡＬＹＳＩＳＯＦＳＴＲＥＳＳＡＮＤＴＥＭＰＥＲＡＴＵＲＥＩＮＴＨＥＣＯＮＦＯＲＭＦＯＲＭＩＮＧＰＲＯＣＥＳＳ——ＦＯＵＮＤＡＴＩＯＮＴＨＥＯＲＹＰｅｎｇＹｕｅｌｉｎＨｕＪｉａｎＭｏＢｉｎ（ＤｅｐａｒｔｍｅｎｔｏｆＡｐｐｌｉｅｄＭａｔｈｅｍａｔｉｃ...     

电脑座便器计算机自动测试系统

性能特点： 1〕系统由一台主控微机/工作站和5～8台下位机构成，可同时对5～8个产品进行质量检测。 2〕主控工作站可对多道检测信号进行实时在线监测。 3〕根据预定检测策略，由计算机对检测产品进行质量指标自动判决，无需人工干涉。 4〕全中文窗口图形界面，配备操作容错性能，使用方便。 5〕检测数据自动入库，无需人为操作。 6〕同时支持检测数据的波形打印 7〕配备数据搜索引擎，可对过去5～10年的检测数据进行查询回放，同时按照设定要求可生成日、月、季度和年度生产 质量报表，为生产质量管理部门的分析决策提供有力工具。 8〕系统设置灵活，可随时按照新的要求更改系统的工作流程，可广泛用于其它产品的出厂质量检测。 9〕支持wINNT,WIN 98／2000操作系统。 10〕系统价格低廉，维护简易，性能价格比较高。 应用范围：工业流水线产品中低频信号的质量指标检测。 开发单位：浙江星星集团，上海复旦大学 应用项目负责人：陈忠民联系地址：上海复旦大学电子工程系 200433联系电话：021-65642753     

馈线的故事

馈线与接头的故事,这个题目我想了很久,因为专业术语很枯燥,一度害怕自己中途放弃。在无线通信中,馈线和接头的地位不容忽视,笔者希望尽量使用通俗的语言来表达,让更多朋友可以了解这些繁琐的专业术语。很多朋友认为用台好机器加上高增益天线就是最高配置,对于馈线和接头没什么概念。馈线看似简单的外表下其实蕴含着很多高科技,今天笔者就给您逐步解剖馈线,给您做更为详细的说明。     

SELECTION OF PROPER EMBEDDING DIMENSION IN PHASE SPACE RECONSTRUCTION OF SPEECH SIGNALS

In phase space reconstruction of time series, the selection of embedding dimension is important. Based on the idea of checking the behavior of near neighbors in the reconstruction dimension, a new method to determine proper minimum embedding dimension is constructed. This method has a sound theoretical basis and can lead to good result. It can indicate the noise level in the data to be reconstructed, and estimate the reconstruction quality. It is applied to speech signal reconstruction and the generic embedding dimension of speech signals is deduced.