Sparse-array Synthetic Impulse and Aperture Radar (SIAR) can isotropically radiate by employing multiple frequencies (synthetic pulse) and multiple antennas (synthetic antenna). According to Ambiguity Function(AF), it...Sparse-array Synthetic Impulse and Aperture Radar (SIAR) can isotropically radiate by employing multiple frequencies (synthetic pulse) and multiple antennas (synthetic antenna). According to Ambiguity Function(AF), its range resolution depends only on bandwidth of transmitted signals, however, the distance grating lobes emerge when increasing the time-bandwidth product of transmitted signals. The performance of pulse compression is analyzed with the transmitted signals modulated by phase-coded sequences. It is seen that greater ratio of pulse compression and suppression of range sidelobe in SIAR can be obtained, and its effective range and range resolution is increased as well.展开更多
Impulse components in vibration signals are important fault features of complex machines. Sparse coding （SC） algorithm has been introduced as an impulse feature extraction method, but it could not guarantee a satisf...Impulse components in vibration signals are important fault features of complex machines. Sparse coding （SC） algorithm has been introduced as an impulse feature extraction method, but it could not guarantee a satisfactory performance in processing vibration signals with heavy background noises. In this paper, a method based on fusion sparse coding （FSC） and online dictionary learning is proposed to extract impulses efficiently. Firstly, fusion scheme of different sparse coding algorithms is presented to ensure higher reconstruction accuracy. Then, an improved online dictionary learning method using FSC scheme is established to obtain redundant dictionary and it can capture specific features of training samples and reconstruct the sparse approximation of vibration signals. Simulation shows that this method has a good performance in solving sparse coefficients and training redundant dictionary compared with other methods. Lastly, the proposed method is further applied to processing aircraft engine rotor vibration signals. Compared with other feature extraction approaches, our method can extract impulse features accurately and efficiently from heavy noisy vibration signal, which has significant supports for machinery fault detection and diagnosis.展开更多
This work investigates synchronization of two fractional unified hyperchaotic systems via impulsive control.The stable theory about impulsive fractional equation is studied based on the stable theory about fractional ...This work investigates synchronization of two fractional unified hyperchaotic systems via impulsive control.The stable theory about impulsive fractional equation is studied based on the stable theory about fractional linear system.Then according to the theorem proposed the sufficient condition on feedback strength and impulsive interval are established to guarantee the synchronization.Numerical simulations show the effectiveness of the theorem.展开更多
The evaluation of the minimum distance of linear block codes remains an open problem in coding theory, and it is not easy to determine its true value by classical methods, for this reason the problem has been solved i...The evaluation of the minimum distance of linear block codes remains an open problem in coding theory, and it is not easy to determine its true value by classical methods, for this reason the problem has been solved in the literature with heuristic techniques such as genetic algorithms and local search algorithms. In this paper we propose two approaches to attack the hardness of this problem. The first approach is based on genetic algorithms and it yield to good results comparing to another work based also on genetic algorithms. The second approach is based on a new randomized algorithm which we call 'Multiple Impulse Method (MIM)', where the principle is to search codewords locally around the all-zero codeword perturbed by a minimum level of noise, anticipating that the resultant nearest nonzero codewords will most likely contain the minimum Hamming-weight codeword whose Hamming weight is equal to the minimum distance of the linear code.展开更多
Based on the research on time domain and frequency domain transmitted reference Impulse Radio Ultra-WideBand (IR-UWB) system, this paper studies the optimization design for code domain transmitted reference IR-UWB sys...Based on the research on time domain and frequency domain transmitted reference Impulse Radio Ultra-WideBand (IR-UWB) system, this paper studies the optimization design for code domain transmitted reference IR-UWB system, and proposes a modified code domain transmitted reference IR-UWB system. The Bit Error Rate (BER) expressions for the modified system model in the condition of Additive White Gaussian Noise (AWGN) and multipath fading are deduced respectively. In addition, the performances of the modified system and the other three transmitted reference IR-UWB systems are simulated and compared. Theoretical analysis and simulation results show that the performance of the modified system is superior to the other three systems.展开更多
文摘Sparse-array Synthetic Impulse and Aperture Radar (SIAR) can isotropically radiate by employing multiple frequencies (synthetic pulse) and multiple antennas (synthetic antenna). According to Ambiguity Function(AF), its range resolution depends only on bandwidth of transmitted signals, however, the distance grating lobes emerge when increasing the time-bandwidth product of transmitted signals. The performance of pulse compression is analyzed with the transmitted signals modulated by phase-coded sequences. It is seen that greater ratio of pulse compression and suppression of range sidelobe in SIAR can be obtained, and its effective range and range resolution is increased as well.
基金国家自然科学基金面上项目(60970058)江苏省现代企业信息化应用支撑软件工程技术研发中心开放基金项目(SX200906)+1 种基金The National Natural Science Foundation of China(No.60970058)The Opening Project of Jiangsu Province Support Software Engineering R&D Center for Modern Information Technology Application in Enterprise(No.SX200906)
基金supported by the National Natural Science Foundation of China (No. 51201182)
文摘Impulse components in vibration signals are important fault features of complex machines. Sparse coding （SC） algorithm has been introduced as an impulse feature extraction method, but it could not guarantee a satisfactory performance in processing vibration signals with heavy background noises. In this paper, a method based on fusion sparse coding （FSC） and online dictionary learning is proposed to extract impulses efficiently. Firstly, fusion scheme of different sparse coding algorithms is presented to ensure higher reconstruction accuracy. Then, an improved online dictionary learning method using FSC scheme is established to obtain redundant dictionary and it can capture specific features of training samples and reconstruct the sparse approximation of vibration signals. Simulation shows that this method has a good performance in solving sparse coefficients and training redundant dictionary compared with other methods. Lastly, the proposed method is further applied to processing aircraft engine rotor vibration signals. Compared with other feature extraction approaches, our method can extract impulse features accurately and efficiently from heavy noisy vibration signal, which has significant supports for machinery fault detection and diagnosis.
基金Key Creative Project of Shanghai Education Community,China(No.13ZZ050)Key Basic Research Project of Shanghai,China(No.12JC1400400)
文摘This work investigates synchronization of two fractional unified hyperchaotic systems via impulsive control.The stable theory about impulsive fractional equation is studied based on the stable theory about fractional linear system.Then according to the theorem proposed the sufficient condition on feedback strength and impulsive interval are established to guarantee the synchronization.Numerical simulations show the effectiveness of the theorem.
文摘The evaluation of the minimum distance of linear block codes remains an open problem in coding theory, and it is not easy to determine its true value by classical methods, for this reason the problem has been solved in the literature with heuristic techniques such as genetic algorithms and local search algorithms. In this paper we propose two approaches to attack the hardness of this problem. The first approach is based on genetic algorithms and it yield to good results comparing to another work based also on genetic algorithms. The second approach is based on a new randomized algorithm which we call 'Multiple Impulse Method (MIM)', where the principle is to search codewords locally around the all-zero codeword perturbed by a minimum level of noise, anticipating that the resultant nearest nonzero codewords will most likely contain the minimum Hamming-weight codeword whose Hamming weight is equal to the minimum distance of the linear code.
基金Supported by the National High Technology Research and Development Program of China(863 Program)(No.2009AA011205)the Important National Science and Technology Specific Projects(No.2009ZX03006-008)
文摘Based on the research on time domain and frequency domain transmitted reference Impulse Radio Ultra-WideBand (IR-UWB) system, this paper studies the optimization design for code domain transmitted reference IR-UWB system, and proposes a modified code domain transmitted reference IR-UWB system. The Bit Error Rate (BER) expressions for the modified system model in the condition of Additive White Gaussian Noise (AWGN) and multipath fading are deduced respectively. In addition, the performances of the modified system and the other three transmitted reference IR-UWB systems are simulated and compared. Theoretical analysis and simulation results show that the performance of the modified system is superior to the other three systems.
