Applied Mechanics and Materials Vols. 427-429

Abstract: Starting from pseudo-random interleaver and parallel convolution respectively, this paper has proposed a simple and fast LDPC encoding method without the loss of BER performance. when we use S-random interleaver, it has a good adaptation in both Gaussian noise channel and Rayleigh fading channel. And it can conduct random pre-encoding directly and does not need to look up for 4-cycles. Even if the number of iterations is low, its performance also remains stable.

Abstract: In view of the slow match speed of the image, the article proposes gray genetic algorithm (GGA), one kind of new fast image match method, combining the gray connection theory with genetic algorithm. This method, firstly, determines question's parameter space to obtain several of initial points required to be match through coding the parameter space and the string collection initialized. Then the reference sequence and the comparison sequence separately are to be constructed by means of the template chart and the histogram searching for current subgraph's information. Lastly, fitness function are established on these two sequences between pessimistic interrelatedness as reference Based on this, the string collection initialized evolves gradually optimizing region of the search space after many kinds of genetic algorithm's operation, such as the choice operation, the overlapping operation and the variation operation and so on. Finally, it infinitely approaches the optimum matching position. Because the GGA law has fully applied the small sample and genetic algorithm computation parallelism characterized in the gray connection theory, the timeliness of the image match have been distinctly enhanced with certain match precision.

Abstract: The optimization of degree profiles of low-density parity-check (LDPC) code in additive white Gaussian noise (AWGN) multiple access channel (MAC) by fitting the transfer characteristics of variable nodes detector (VND) and that of check nodes detector (CND) is discussed. Extrinsic information transfer (EXIT) characteristics are used for determining the degree profiles based on curve fitting. The convergence the optimized LDPC code is ensured by the EXIT characteristics of VND and CND. Degree profiles are obtained and check matrix is constructed. Simulation results show that the method is variable in designing LDPC code degree profiles in MAC with reduced complexity compared with density evolution based on Gaussian approximation.

Abstract: We proposed an improved motion image optical flow method which can artificially adjust and select the threshold value according to the reality condition and different position of the image .Using traditional method,such as Horn-Schunck’s optical flow estimation algorithm,will possibly lead to the problem of losing edge information or obtaining unsmooth optical flow field, when weight coefficient is too big or too small at the same time. The experimental results show that the motion image and its edge are more clear and the value of PSNR and RMSE have been all improved by using the improved algorithm, moreover the improved algorithm will not increase more computation complexity.

Abstract: Frames play an important role in field of the engineering and technology. In this paper, symmetric wave packet frames are constructed, which generalizes the existing result to the general case. This way makes the amount of wavelets largely increase.

Abstract: In the analysis of the characteristics about the microscopic leukocyte image sequence, a kind of grading contrast limited adaptive histogram equalization (GCLAHE) algorithm was presented in the preprocessing. This method can effectively enhance the cell contrast with the surrounding background, and can play a better filtering to eliminate noise effects, at the same time keep better cell boundary information, and then improve the cell tracking rate. 100 frames of continuous images sequence were processed in Matlab 7, the average false detection rate is 0.48%, and the average miss detection rate is 1.20%. It is shown that the algorithm can reduce cell miss detection rate and the false detection rate; improve cell detection and tracking precision.

Abstract: In this paper, we study an information theoretic approach to image similarity measurement for content-base image retrieval. In this novel scheme, similarities are measured by the amount of information the images contained about one another mutual information (MI). The given approach is based on the premise that two similar images should have high mutual information, or equivalently, the querying image should convey high information about those similar to it. The method first generates a set of statistically representative visual patterns and uses the distributions of these patterns as images content descriptors. To measure the similarity of two images, we develop a method to compute the mutual information between their content descriptors. Two images with larger descriptor mutual information are regarded as more similar. We present experimental results, which demonstrate that mutual information is a more effective image similarity measure than those have been used in the literature such as Kullback-Leibler divergence and L2 norms.

Abstract: The problem of spacecraft attitude estimation utilizing star sensors and gyros is considered in this paper. Since the errors of the quaternion outputs of star sensors projected on the direction along the optical axis is higher than the other two directions, a novel method to increase the estimation accuracy of the attitude filter is presented, by producing observation vectors along the direction of the light axes, which are composed of a couple of quaternion outputs from different star sensors. The proposed algorithm is validated and proved more precise by numerical simulations.

Abstract: Distance metric is important for image transform, it reflects the similarity of manifold between pre and post transformation. Tangent distance method is usually used to approximate nonlinear manifolds by its tangent hyperplane in digit recognition; however, it sometimes neglects the high-order statistic information of the image. A new image distance metric is proposed in this paper which is based on Gabor transformation to obtain the Gabor feature vector, then the feature manifold can be approximated by curve surfaces based on second-order Taylor expansion with respect to intrinsic variables, and the distance metric by Gabor transformation is defined as the minimum distance between the approximated curved surfaces in feature observation space. Experiments show that the distance metric based on Gabor transformation and manifold works well on digit recognition, it excelled tangent distance method.

Abstract: Chaos algorithm is essential in weak signal detection because of its sensibility to weak signals and immunity to noise. This paper applies subspace algorithm which originates from array signal processing to weak signal detection field because of its lower signal to noise ratio. Firstly, the article introduces the principles of two algorithms, then analyses simulation experiments results of real signal data. After that, a conclusion for two algorithms comparison by estimation of computation cost, complexity of implementation and hardware resources occupied is drawn. At the end, the writer designs a duffing chaos module which is the core part of chaotic detection with verilog-hdl.