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A robust watermarking algorithm based on QR factorization and DCT using quantization index modulation technique
Hong-yuan Chen, Yue-sheng Zhu
Front. Inform. Technol. Electron. Eng., 2012, 13(8): 573-584.
https://doi.org/10.1631/jzus.C1100338
We propose a robust digital watermarking algorithm for copyright protection. A stable feature is obtained by utilizing QR factorization and discrete cosine transform (DCT) techniques, and a meaningful watermark image is embedded into an image by modifying the stable feature with a quantization index modulation (QIM) method. The combination of QR factorization, DCT, and QIM techniques guarantees the robustness of the algorithm. Furthermore, an embedding location selection method is exploited to select blocks with small modifications as the embedding locations. This can minimize the embedding distortion and greatly improve the imperceptibility of our scheme. Several standard images were tested and the experimental results were compared with those of other published schemes. The results demonstrate that our proposed scheme can achieve not only better imperceptibility, but also stronger robustness against common signal processing operations and lossy compressions, such as filtering, noise addition, scaling, sharpening, rotation, cropping, and JPEG/JPEG2000 compression.
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Negative effects of sufficiently small initial weights on back-propagation neural networks
Yan Liu, Jie Yang, Long Li, Wei Wu
Front. Inform. Technol. Electron. Eng., 2012, 13(8): 585-592.
https://doi.org/10.1631/jzus.C1200008
In the training of feedforward neural networks, it is usually suggested that the initial weights should be small in magnitude in order to prevent premature saturation. The aim of this paper is to point out the other side of the story: In some cases, the gradient of the error functions is zero not only for infinitely large weights but also for zero weights. Slow convergence in the beginning of the training procedure is often the result of sufficiently small initial weights. Therefore, we suggest that, in these cases, the initial values of the weights should be neither too large, nor too small. For instance, a typical range of choices of the initial weights might be something like (?0.4, ?0.1)∪(0.1,0.4), rather than (?0.1, 0.1) as suggested by the usual strategy. Our theory that medium size weights should be used has also been extended to a few commonly used transfer functions and error functions. Numerical experiments are carried out to support our theoretical findings.
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An iterative linear quadratic regulator based trajectory tracking controller for wheeled mobile robot
Hao-jie Zhang, Jian-wei Gong, Yan Jiang, Guang-ming Xiong, Hui-yan Chen
Front. Inform. Technol. Electron. Eng., 2012, 13(8): 593-600.
https://doi.org/10.1631/jzus.C1100379
We present an iterative linear quadratic regulator (ILQR) method for trajectory tracking control of a wheeled mobile robot system. The proposed scheme involves a kinematic model linearization technique, a global trajectory generation algorithm, and trajectory tracking controller design. A lattice planner, which searches over a 3D (x, y, θ) configuration space, is adopted to generate the global trajectory. The ILQR method is used to design a local trajectory tracking controller. The effectiveness of the proposed method is demonstrated in simulation and experiment with a significantly asymmetric differential drive robot. The performance of the local controller is analyzed and compared with that of the existing linear quadratic regulator (LQR) method. According to the experiments, the new controller improves the control sequences (v, ω) iteratively and produces slightly better results. Specifically, two trajectories, ‘S’ and ‘8’ courses, are followed with sufficient accuracy using the proposed controller.
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Developing a multi-objective, multi-item inventory model and three algorithms for its solution
Ommolbanin Yousefi, Mirbahadorgholi Aryanezhad, Seyed Jafar Sadjadi, Arash Shahin
Front. Inform. Technol. Electron. Eng., 2012, 13(8): 601-612.
https://doi.org/10.1631/jzus.C1100384
We develop a multi-objective model in a multi-product inventory system. The proposed model is a joint replenishment problem (JRP) that has two objective functions. The first one is minimization of total ordering and inventory holding costs, which is the same objective function as the classic JRP. To increase the applicability of the proposed model, we suppose that transportation cost is independent of time, is not a part of holding cost, and is calculated based on the maximum of stored inventory, as is the case in many real inventory problems. Thus, the second objective function is minimization of total transportation cost. To solve this problem three efficient algorithms are proposed. First, the RAND algorithm, called the best heuristic algorithm for solving the JRP, is modified to be applicable for the proposed problem. A multi-objective genetic algorithm (MOGA) is developed as the second algorithm to solve the problem. Finally, the model is solved by a new algorithm that is a combination of the RAND algorithm and MOGA. The performances of these algorithms are then compared with those of the previous approaches and with each other, and the findings imply their ability in finding Pareto optimal solutions to 3200 randomly produced problems.
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Development of a direct current power system for a multi-node cabled ocean observatory system
Yan-hu Chen, Can-jun Yang, De-jun Li, Bo Jin, Ying Chen
Front. Inform. Technol. Electron. Eng., 2012, 13(8): 613-623.
https://doi.org/10.1631/jzus.C1100381
Due to the shortage of suitable research methods for real-time and long-term observation of oceans, an innovative approach that can provide abundant power and wide bandwidth is being developed worldwide for undersea instruments. In this paper, we develop a direct current (DC) power system which is applied to a multi-node cabled ocean observatory system named ZERO (Zhejiang University Experimental and Research Observatory). The system addresses significant issues ranging from terrestrial facility to subsea infrastructure, and focuses on using appropriate methods to deal with several key challenges, including delivery, conversion, distribution, and management of power, and heat dissipation in pressure vessels. A basic laboratory platform consisting of a shore station, a primary node in a water tank, and a secondary node in a deep-sea simulation chamber under 42 MPa pressure was built and fully tested. An improved secondary node was deployed in Monterey Bay in California for a deep-sea trial. An 11-day laboratory test and a half-year sea trial proved that the DC power system based on our proposed methods is viable for the underwater multi-node observatory system.
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8 articles
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