Advanced Materials Research Vol. 981

Abstract: Projector calibration can be seen as a special case of the camera calibration. It can establish the relationship of the three dimensional space coordinates for points and projector image coordinates for points DMD by using a projector to project coding pattern. In camera calibration, ZHANG’s self-calibration was conducted in the maximum likelihood linear refinement. Operation process takes the lens distortion factors into account finding out the camera internal and external parameters finally. Using this algorithm to the projector calibration can solve the traditional linear calibration algorithm which is complex and poor robustness. Otherwise, it can improve the practicability of calibration method. This method can both calibrate the internal and external parameters of projector, which can solve the problem of independently inside or outside calibration.

Abstract: To solve the problem that many image segmentation methods cannot be applied to forward looking sonar image accurately, an improved level set segmentation method was proposed in this paper. Firstly, the level set evolution without re-initialization was introduced. Secondly the different characteristics of forward looking sonar image from the optical image were analyzed, and we got the factors affecting segmentation. Then, to overcome these negative effects, this paper did preprocessing by morphological top-hat and bottom-hat transformation, and carried on level set method without re-initialization to construct an improved level set sonar image segmentation system. Finally, our method was compared with the traditional level set method in computer experiments. Simulation results show that it is more adapted to forward looking sonar image segmentation.

Abstract: An image encryption based on elementary cellular automata was proposed in [Yu Xiao yang et al., International Journal of Security and Its Applications Vol.7, No.5 (2013), pp.397-406.]. In this paper, we analyze the security weaknesses of their algorithm. Based on the given analysis, it is demonstrated that the scheme under study can be broken by various attacks (Chosen Plaintext and Chosen ciphertext attacks).

Abstract: In this paper, first detect the edge of the tongue, to obtain the edge of tongue body coordinates. Then split the tongue using a variety of curve fitting function to analysis plumpness and slenderness of tongue, and compare the accuracy of different curve fitting. Finally, classify the fat tongue and thin tongue by using the neural network.

Abstract: The Beidou (BD) satellite navigation & orientation system is so important of national information infrastructure for our country. After research the BD system in the timing area, whlie analysed the advantage of the Beidou satellite timing technology compared with other conventional timing method, combined with high precision timing experiment and depending on the Common-view experimental results proved that the beidou statllite navigation & orientation system has high research value.

Abstract: £o Based on judging the change of pulse amplitude of phase detecting, a new method of time domain coherency for the radar emitter sorting is proposed in this paper. We analyzed the theory of the signal coherency recognition method. Then, the mathematic derivation process and specific recognition steps of the new method are detailedly given. But above all, the new method can be applied into the signal sorting of radar emitter. Simulation results also reveal that this new method can effectively sort the radar emitter signals under the low signal-to-noise ratio, and it is a huge help to solve the problem of " leakage-batch ". Results demonstrate that the new method has strong theoretical value.

Abstract: The study of GPS L2C signal tracking algorithm aims to realize signal tracking in poor environment. The main topic includes L2C signal tracking principle and the performance of real signal tracking. The structure and applied background of the signal is stated in the introduction at first. The characteristic of time division multiplexing of CM code and CL code makes this tracking method utilize half of received energy inevitably. Then, as compositions of L2C signal tracking algorithm, the data demodulation, the code tracking and the carrier tracking module are showed their details in the paper, including the structure of the DLL tracking loop, the Costas carrier tracking loop and some necessary computational principles. Finally, compare happens on real excellent and poor signal-to-noise ratio environments by setting suitable parameters including the sampling frequency, the center frequency and the pseudo code rate to prove the effectiveness of tracking algorithm.

Abstract: A method to design and implement digital communication platform was in introduced in this paper. The platform based on software radio method can change modulation method conveniently without the change of hardware system because it used FPGA and DSP to do modulation and signal process. The QPSK modulation and demodulation was implemented in the platform to test this platform.

Abstract: This article introduces the basic principle and theory model of the crossbeam space power synthesis, and presents the result of system simulation and analysis. The author has adopted random sparse disposal and compounded the multi-points sources of transmitted power in space, through controlling the accurate orientation of the beam, reaching the aim of enhancing power. Meantime, arbitrary distributed array has been adopted to make the system more practical.

Abstract: Gain-flatness is one of the crucial parameters for the application of fiber Raman amplifier (FRA). To obtain the ideal gain-flatness within the wide spectrum, the devices should be optimized in a FRA system. In this article, rather than a complicated design reported in the traditional schemes, we adopt a single-wavelength laser diode to flatten the gain spectrum of FRA through optimize its pumping power and wavelength simply. The numerical results by simulation show that the gain-flatness of the designed FRA system is controlled within ±1 dB in the range of 1500 nm ~1560 nm by a laser diode with 1435 nm and 250 mW.