Applied Mechanics and Materials Vols. 644-650

Abstract: Segmentation algorithm of CT Image is discussed in this paper. Dynamic relative fuzzy region growing algorithm is used for CT. At the beginning of the segmentation, the confidence interval region growing algorithm is used. The overlapping parts in the initial segmentation result is segmented again with the improved fuzzy connected, and then determine which region the overlapping parts belong to. Thus, the final segmentation result can be obtained. Since the algorithm contains the advantages of region growing algorithm, fuzzy connected algorithm and the region competition, the runtime of segmentation is greatly reduced and better experimental results are obtained.

Abstract: In this paper, twisted differential lines on multi-layer PCB is modeled with 3D Full-wave EM tool, and crosstalk is analyzed based on mix-mode S parameters. It is compared with traditional differential microstrip line. Then the simulation results demonstrate that twisted differential lines on multi-layer PCB can enhance immunity against crosstalk .

Abstract: Shape is the inherence characteristic of an object in the image, and it is the important character used for the object recognition. So it is significant for object recognition based on shape. This paper presents a contour-based method of feature extraction and shape recognition. First the object contour is translated into a 1-D contour curve. Secondly the curve is smoothed to restrain the noise. The number of peaks of the curve is achieved as well as the areas which contained between adjacent peak-valley, then the latter is followed by Discrete Fourier Transformation (DFT). Then two kinds of features ate extracted which are invariant to translation, scaling and rotation transformations. By using the features, a two-stake recursive algorithm for recognition is proposed. Experimental results show that this method is simple and efficient.

Abstract: A new transient spectrum detection method with high time resolution based on area CCD is proposed. By reforming and mending working sequence of CCD, utilizing principle of frame restore, linear spectrum detection with high time resolution was achieved. This method improves frame rate and time resolution of CCD greatly. LED impulse light experiment is performed to demonstrate feasibility of the method. Experiment results show that this transient spectrum acquisition method based on area CCD is efficacious, detection frame rate can be as high as 10Mfps. Time resolution is less than 100ns, and can be able to image 2048 times continuously. The experiment is of importance to expand application of CCD in the transient spectrum detection area.

Abstract: In sky-wave over-the-horizon radar system, it is difficult to detect ship because the Doppler shift of the ship is very close to the strong ocean clutter. Traditional clutter cancellation algorithms suppress ocean clutter by estimating clutter parameters and removing the clutter signal in time domain. However, they estimate the clutter parameters by the maximum value of the post DFT spectrum and thus lead to the low accuracy. In this paper, a modified clutter cancellation algorithm is proposed, which corrects estimated frequency by utilizing the three maximum spectrum values and overcomes the poor cancellation performance caused by inaccurate estimation of clutter parameters. Compared with traditional clutter cancellation algorithm, the proposed algorithm can get more accurate clutter parameters and reduce the energy and expansion of the remaining clutter. Simulation demonstrated that the proposed algorithm had a better clutter cancellation performance compared to the traditional ones.

Abstract: The parameter estimation of the Polynomial Phase Signals (PPS) is one of the core issues. In this paper, UKF-based algorithm is proposed to estimate the parameter of PPS embedded in Gaussian noise. The algorithm constructs an adequate state-space model to represent the PPS and the model can also be implied in real radar signal. Unscented Kalman filtering is applied to estimate the signal parameters. The method achieves the lower SNR threshold, the faster convergence speed, the higher accuracy and more stable estimation performance compared with the existing methods. Simulation also verifies the efficiency of the proposed method.

Abstract: Aiming at problems meet in the copyright of H.264/AVC video, a method of digital watermarking based on intra prediction coding. The method combines wavelet transforms, chaos theory and spread spectrum modulation to preprocess grayscale image. Then according to different intra prediction mode of I-frame brightness sub block, selects different DCT coefficient, and embeds the watermark information by improved LSB algorithm. Experiments show that, this method ensures video effects without distortion, high blind detection accuracy, and little effect on code rate.

Abstract: Texture compression technology is an effective way to improve the capacity of the texture without increasing the texture memory. This paper studies a texture compression method based on mipmap technology, details several texture compression formats, and describes the texture file of several formats generating and corresponding parameters adjustment. Practical results show that the texture compression method based on mipmap technology can not only achieve high texture compression ratio, but also cause no effect on the texture quality.

Abstract: The matched filter of chaotic radar system proposed by Ned J. Corron can be implemented through low-cost analog devices. But the spectrum of transmitted signal of this system is dispersion, causing signal in the process of propagation prone to spectrum leaked. To solve the problem, this paper proposes a low-cost signal design method. In transmitter, making chaotic signal become a band-limited signal by filtering to shape the spectrum; in receiver, using synchronization and filtering to recover the chaotic signal. The proposed method is implemented with low-cost analog devices; in addition, the method is still valid when the SNR is as low as-20dB.

Abstract: For target tracking of agile digital array, we propose a novel model called alternate array. The model means that total array is divided into vertical subarray at the present moment, and vertical subarray is transformed into horizontal subarray at the next moment, then the subarray comes to the first subarray divisions, and so on. Alternate array gives rise to differences of statistical characters of measurement error. Filtering performance is influenced by the feature of measurement data. In the paper, we come up with a new method based on Kalman filter (KF) to solve the difficulty. The new method merges pre-processing and data fusion thought together. Simulation results demonstrate the validity of the proposed algorithm.