Local Feature Based Geometric-Resistant Image Information Hiding

Watermarking aims to hide particular information into some carrier but does not change the visual cognition of the carrier itself. Local features are good candidates to address the watermark synchronization error caused by geometric distortions and have attracted great attention for content-based image watermarking. This paper presents a novel feature point-based image watermarking scheme against geometric distortions. Scale invariant feature transform (SIFT) is first adopted to extract feature points and to generate a disk for each feature point that is invariant to translation and scaling. For each disk, orientation alignment is then performed to achieve rotation invariance. Finally, watermark is embedded in middle-frequency discrete Fourier transform (DFT) coefficients of each disk to improve the robustness against common image processing operations. Extensive experimental results and comparisons with some representative image watermarking methods confirm the excellent performance of the proposed method in robustness against various geometric distortions as well as common image processing operations.

基于谓词不变性的状态反馈控制在机器人遥操作中的应用

传统的基于事件遥操作系统虽然巧妙地避开了变化时延问题[8] ,但是它具有“走走停停”的特点 ,即机器人将当前状态发送出去之后直到操作者的下一个指令到来之前机器人必须保证状态没有变化。对此本文首次提出了利用基于谓词不变性的状态反馈控制来对原有的方法进行改进 ,使机器人能够对动态环境具有适应性

不同类型量表的线上调查和传统纸笔调查的比较研究

During the past 11 years, with the rapid development of the Internet, more and more psychologists began to realize and take advantage of it, which led to a growing number of psychological test administrated on the internet for data collection. But there were some controversy about the reliability and representatively of this new method. To examine the applicability of the Online Survey and how different types of scales used on the internet, we first reversed the measurement instrument, then from three different levels to investigate the equivalence of online survey and paper-and-pencil assessment, namely, sample level, scale level and item level. Both Classical Test Theory and Item Response Theory were used to analyze the invariance of different types of scale applicability on the internet. The main conclusions of this study could be drawn as follows: 1. In the sample-based study, self-select sample of the online survey was compared to the random sampled sample of paper-and-pencil assessment. The results showed there were no gender difference between them (p>0.05), but the online survey sample was characterized with high qualifications, high-income and younger features (88% of the sample with post-secondary education or above, and 71% aged 20 -29 years). There were significant differences on the scores of all scales between online survey and paper-and-pencil assessment (p<0.01). With demographic controlled, there was no significant difference on the variable of Neurotic between different surveys (p>0.05). 2. With in-group design, it was proved equivalence of the scale of BI (Attitude toward Brand Importance), BT (Attitude toword Brand Switcher), Extraversion, and Conscientiousbess in the compared study in the reliability, construct validity and average scores. 3. On the item level, the results based on the Item Response Theory analysis showed that 2PLM is appropriate for personality and attitude scales. With regard to personality scale, there emerged some items with DIF in the dimensions of Openness to the experience subscale and Agreeable subscale. However, there were no significant differences about the test function. 4. Exploring the psychometrics properties of answer formats of five-, six-, seven-, ten-points, it was showed that different measurement validity between online survey and paper-and-pencil test. It was also described the lower reliability and validity of six-point scale. In conclusion, the results support the application of personality scale online, but for attitude scale, we need to choose prudently.

Time-dependent wavepacket approach to the influence of intense fields on the population of molecular excited states

The influence of laser-field parameters, such as intensity and pulse width, on the population of molecular excited state is investigated by using the time-dependent wavepacket method. For a two-state system in intense laser fields, the populations in the upper and lower states are given by the wavefunctions obtained by solving the Schrodinger equation through split-operator scheme. The calculation shows that both the laser intensity and the pulse width have a strong effect on the population in molecular excited state, and that as the common feature of light-matter interaction (LMI), the periodic changing of the population with the evolution time in each state can be interpreted by Rabi oscillation and area-theorem. The results illustrate that by controlling these two parameters, the needed population in excited state of interest can be obtained, which provides the foundation of light manipulation of molecular processes. (C) 2005 Elsevier B.V. All rights reserved.