Applied Mechanics and Materials Vols. 644-650

Abstract: To locate the imaging slice, the hydrogen protons within the selected slice are excited by the coaction of radio-frequency pulse (RF pulse) and slice-selection gradient during the process of magnetic resonance imaging (MRI). However, the absolute consistency of the time between the RF transmitting system and gradient system can’t be guaranteed in an actual magnetic resonance system, which makes the slice profile not ideal enough. Imperfect slice profile will lead to poor imaging quality. In this paper, Shinnar-Le Roux (SLR) theory is used to simulate the slice profile with different relative delays between RF and slice-selection gradient to solve this problem. By matching the actual slice profile with the simulation results, the relative delay is measured in an actual 0.35T permanent magnet MRI system. The practicability of the method is verified for the improvement of image quality after applying the measured delay to correct the actual MRI system.

Abstract: The compatible receiver for satellite navigation is the trend of the receiver along with appears a variety of satellite navigation system. The basic structure of carrier NCO and PN code NCO was designed according to the parameters which are determined on the basis of the introduced theory of reconfigurable carrier NCO and PN code NCO. The hardware testing of the designed carrier NCO and PN code NCO had finished in the end, and the result shows that the carrier NCO of and PN code in accordance with the design parameters; therefore ,the design can process dissimilar navigating signal, which is used in the channel processing of reconfigurable navigating signal directly. It is a firm base of researching and exploiting compatible receiver for a variety of satellite navigation system in the future.

Abstract: Firstly, this paper introduces the common methods and accounts for the advantage of ionosphere grid products for correcting ionosphere errors with single-frequency GPS, according the analysis that ionosphere grid product can effectively ameliorate errors of single-frequency GPS navigation and positioning. In detail, this article gives the establishment, forecast and operation methods of ionosphere grid products, and introduces the method that calculates the VTEC (Vertical Total Electronic Contents) values of the geocentric latitude of the ionospheric pierce point, the VTEC values of four-point interpolation models and the single-layer mapping function. It’s also compares different pairs of ionosphere correction data and satellite ephemeris which use to analyze the impact of real-time positioning accuracy of single-frequency GPS. The experiments prove that the predicted ionosphere grid products can obviously improve the precision for single-frequency users, and have some practical values for single-frequency positioning and orbit determination.

Abstract: This paper presents a new method for strong background noise of known frequency signal estimation method is then applied to the demodulated digital FM signal. This new method only needs to know the frequency of the demodulated carrier signal phase information without the need to complete the digital FM demodulation signal. Computer simulations show that the method has more than non-coherent demodulation noise immunity, and has a very strong ability of anti-phase fluctuations. Thus, the demodulation method has good prospects for engineering applications.

Abstract: Spread spectrum communication system wideband interference suppression technique has drawn increasing attention. In this paper, the typical broadband interference signal interference LFM (Linear Frequency-Modulated, LFM), for example, the results of research focus and reviews the current direct sequence spread spectrum (Direct Sequence Spread Spectrum, DSSS) system wideband interference suppression.

Abstract: In order to detect visually salient regions in video sequences, a motion saliency detection method is proposed. The motion vectors of each video frame is used to get two motion saliency features. One represents the uniqueness of the motion,and the other one represents the distribution of the motion in the video scene. Then, the Gaussian filtering is conducted to combine the two feature to make the motion saliency map, in which the salient regions or objects in the video sequences could be detected. The experimental results show that the proposed method could achieve excellent saliency detection performances.

Abstract: Facing asymmetric threats in a network centric environment, modern naval command and control systems confront increasingly demanding challenges in data fusion. It is very important to efficiently and promptly predict the enemy’s or adversary tactical intention from level 2 data fusion. In this paper, a layered intention model is proposed to represent the uncertain elements relating to adversarial intention and their uncertain relations in naval battlefield domain. The main ideal of this paper is to develop a hierarchical Bayesian network based on situation-specific Bayesian network (SSBN) and dynamic Bayesian network (DBN) that can be adapted to cope with the multi-timescales layered intention recognition problem.

Abstract: The design of large-scale video tracking software system is studied. With the continuous development of computer video processing technology, large-scale video tracking technology has become very important. This paper presents a design method for large-scale video tracking software system based on Radon detection algorithm. During the video tracking process, numerous video images need to be collected, and then preprocessed with filtering algorithm, through Radon detection method to predict and compensate moving objects trajectory obtained in video to make up for the tracking lag caused by mutated direction. Experimental results show that the proposed algorithm for large-scale video tracking software design can improve the tracking accuracy effectively, and achieve satisfactory results.

Abstract: Port surveillance videos are degraded seriously in foggy conditions. This paper presented a clearness algorithm based on wavelet packet decomposition. Firstly, we extracted the background image from degraded videos and established the updated model; Secondly, we detected the moving objects as foreground images; Thirdly, we defogged these images based on wavelet packet decomposition; Finally, we fused the background and foreground images together. The experimental results show that our method is more effective.

Abstract: ion generation based on face detection and recognitionXiaokang Wu^{1, a}, Chenggang Xie^{2, b}, Qin Lu^{2, c1} National University Of Defense Technology, Changsha 410073, China;^a172896292@qq.com, ^bqingqingzijin_k@126.com,Keywords: face detection, face recognition, key frame, video abstractionAbstract. In order to facilitate users browse the behaviors and expressions of interesting objects in a video quickly, need to remove the redundancy information and extract key frames related to the object interested. This paper uses a fast face detection based on skin color, and recognition technology using spectrum feature matching, decompose the coupling video, and classify frames related to the object into different sets, generate a different video abstraction of each object. Experimental results show that the algorithm under different light conditions has better practicability.