Embedding Position Research Articles

A chaos-based self-embedding secure watermarking algorithm

This paper presents a novel chaos-based self-embedding secure watermarking algorithm based on the chaotic pseudorandom ness and sensitivity to initial value of chaotic map. In the proposed approach, the real-valued chaotic sequence, which is generated by the given initial value as secret key, is used to produce the ordered indices as the watermark embedding positions. The proposed algorithm has a larger key space than the existing self-embedding watermarking algorithms due to its watermark embedding positions being randomly selected by the secret key. Furthermore, the problem, how to locate the tampered image block in the self-embedding watermarking algorithm has been solved successfully. Theoretical analysis and simulation results show that our scheme not only improves the abilities of tamper localization, but also has better security against many attacks, including the vector quantization and synchronous counterfeiting attacks.

Color image authentication based on spatiotemporal chaos and SVD

In this paper, a new semi-fragile watermarking scheme for color image authentication is proposed based on spatiotemporal chaos and SVD (singular value decomposition). Wavelet transform is applied to watermarking. In contrast to conventional approaches where the watermark is embedded directly on the wavelet coefficients, we embed the watermark onto the SVs (singular values) of the blocks within wavelet subband. In order to enhance the security, spatiotemporal chaos is employed to select the embedding positions for each watermark bit as well as for watermark encryption. The experiment results show that the proposed scheme is able to identify malicious attacks to the image, while is robust to JPEG compression. And due to the sensitivity to the initial conditions of the spatiotemporal chaos, the security of the scheme is greatly improved.

광섬유 브래그 격자를 이용한 촉각센서용 유연 단위 힘 센서 개발

This paper describes the flexible force sensor using fiber Bragg grating (FBG) and silicone rubber for the tactile sensation to detect the distributed normal force. The newly designed FBG flexible force has simple structure and can be easily multiplexed with simple wiring compared with the other electric mechanical sensors. We designed the flexible silicone rubber transducer and found the optimum embedding position of FBG in the transducer using the finite element analysis. This flexible force sensor has good performance and is immunity to the electromagnetic field compared with any other kinds of small force sensors for tactile sensation.

Correlation-Based Video Watermarking Method Using Inter-Frame Similarity

This paper presents a correlation-based watermarking method for video using the similarity of adjacent frames. In general, the adjacent frames of a video sequence is very similar. In the proposed scheme, we use an adjoining frame in detection process instead of an original image in the watermarking scheme of Cox et al. So the proposed method does not need an original video sequence in detection process. When a watermarked video sequence is attacked by overwriting copy or frame dropping, the pair of the frames that is not adjoining in an original video sequence is used in detection process. However, since a watermark is embedded in a part of each frame and embedding positions are different for each frame in the proposed method, we can detect the watermark even from an overwriting-copied video sequence and a frame-dropped video sequence. Experimental results show that the proposed method is robust against overwriting copy and frame dropping. Moreover, it is shown from experimental results that the method has robustness to low bitrate MPEG compression and StirMark attack.

A Novel Blind Video Watermarking Scheme Based on Independent Dynamic Component

Video copyright protection has become important as it is possible to make unlimited copies of digital video without quality loss. Video watermark is the main method of video copyright protection. A novel blind video watermarking scheme is proposed in this paper, in which independent component analysis (ICA) is used to extract the common static component and relative dynamic component from the consecutive frames. And then a designed watermark is embedded into the wavelet coefficients of the obtained dynamic component according to the 4-neighboring-mean based algorithm. The binarization of the 3-level-approximate sub-image of the I-frame in each GOP (GOP-Group of Picture) is selected as the watermark for this GOP. Given such watermark, the scheme can easily resist copy attack and temporal synchronization. Besides, because the watermarks of different GOPs and their embedding positions in a GOP are different, the intra-video collusion attack can be resisted effectively and there is no possibility for inter-video collusion attack to succeed. The simulation shows the feasibility of this scheme, which can resist well temporal synchronization, copy attack, and collusion attack.

Highly robust watermarking scheme based on surrounding mean value relationship

A watermarking algorithm operated in the wavelet transform domain is proposed. For the purpose of security and robustness, we generate a watermark sequence by selectively modifying the middle-frequency parts of images. Meanwhile, we also employ the masking characteristics of the human visual system (HVS) to ensure the watermark invisibility. The watermark data are detected using the embedding position after the wavelet decomposition of the watermarked image. The experimental results show that the proposed scheme is superior to quantization-based methods in terms of transparency, robustness, and computation complexity.

Computational Analysis and Optimization for Smart Patching Repairs

A classical cracked metallic structure, repaired with a ‘smart’ bonded composite patch with embedded optical fibers (to detect the strain field variations of the loaded structure), has been studied here-in. Finite element analysis was used, where-in the composite patch was modeled as a layered structure with three-dimensional elements constituting six different laminae. Each lamina is assumed to have different mechanical properties, according to the studied case, in order to simulate different stacking sequence. A resin rich ‘eye’ pocket has also been modeled in order to simulate the exact form of resin area produced during the manufacturing process. The patch is bonded over a cracked aluminum sheet through a small adhesive layer placed in between. External loads were applied only on the metal structure, as in a real repair case. The primary loading axis of the metal was assumed to be parallel to the direction of the optical fibers. Due to the different nature of the materials that form the composite patch, complex mechanical interactions between the fibers and the surrounding material occur, resulting in a complicated strain field along the optical fiber sensor. This affects the structural integrity of both the patch and the repair. Different optical fiber layer positions were considered, to study their effect on the resulting strain field and the structural integrity of the patch. Analysis concluded that the best available embedding position of an optical fiber in a laminated patch coincides to the one predicted as neutral surface, according to Rose's analytical equations.

Thermal Buckling of Laminated Composite Beams with Embedded Shape Memory Alloy Actuators

In this paper, the thermal buckling and postbuckling behaviours of a composite beam with embedded shape memory alloy (SMA) wires are investigated experimentally and analytically. For the purpose of enhancing the critical buckling temperature and reduction of the lateral deflection on thermal buckling and postbuckling, the characteristics of thermal buckling are investigated through the use of the shape recovery force. The results of thermal buckling tests using uniformly heated and clamped composite beam specimens with embedded SMA wire actuators are discussed. The temperature-load-deflection behaviour records present quantitatively how the shape recovery force affects the thermal buckling behaviour. For this experiment, we considered the initial geometric imperfections, the slenderness ratio of the beam and the embedding position of the SMA wire actuators. The experimental results show that the shape recovery force reduces the thermal expansion of the composite laminated beam. This results in an increase of the critical buckling temperature and a reduction of the lateral deflection of the beams.