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When global navigation satellite system (GNSS) receivers move at a high speed, the directions of arrival (DOAs) corresponding to interferences may change rapidly, which will cause a performance degradation of array antenna. A null widening algorithm based on the interference-plus-noise covariance (INC) matrix reconstruction is proposed. Firstly, the number of interferences is estimated via the ratio between adjacent eigenvalues of the sample covariance matrix. Then, the interference DO As are estimated roughly using the spatial spectrum estimates and the spatial spectrum estimates around interferences are reset according to the required null width. Finally, the INC matrix can be reconstructed with the reset spatial spectrum estimates, based on which the weight vector is sloved. Simulation results show that the proposed algorithm performs better than the other null widening algorithms in the carrier to noise ratio (C/No), by at least 5 dBHz. Meanwhile, the proposed algorithm has a deeper null when the null width keeps the same. [ABSTRACT FROM AUTHOR]

In order to solve the blind estimation problem of the frequency hopping (FH) parameters in the complex electromagnetic environment, an algorithm based on time-frequency variance clustering is proposed. Considering the case where both low signal-to-noise ratio (SNR) and fixed frequency interference exist simultaneously, the signal is transformed into the time-frequency domain by short-time Fourier transform (STFT). The time-frequency interval of the signal is extracted by genetic algorithm, and k-means clustering is performed according to the time-frequency variance. Eliminating noise and fixed-frequency interference, and then extracting time-frequency ridge, the Haar wavelet is used to detect its singularities, furthermore, to estimate parameters such as FH period, hopping speed and hopping frequency. The simulation results show that the proposed algorithm can accurately estimate the parameters such as FH period when the SNR is lower than -5 dB. The correct probability of parameter estimation is over 90%. [ABSTRACT FROM AUTHOR]

Objective: To investigate the treatment effect of laparoscopic hepatectomy and microwave ablation for colorectal liver metastases., Methods: We retrospectively analyzed 126 patients who received treatment for colorectal liver metastases in our hospital during Jan. 2009 to Jan. 2015, and these patients were divided into laparoscopic surgical group (40 cases), microwave group (42 cases) and open surgical group (44 cases). The overall survival rate and disease-free survival rate were compared by using the Kaplan-Meier method., Results: The operation time in three groups were (120±35), (55±20), (100±30) min, respectively. The blood loss in the three groups were (300±120), (100±25), (250±95) ml, respectively. The operation time, blood loss and hospital stay in microwave group were less than the other two groups (P<0.05). There was no significant difference in survival time and postoperative complications in these groups (P>0.05)., Conclusions: Laparoscopic hepatectomy and microwave ablation in the treatment of colorectal liver metastases is effective compared to open hepatectomy. So the minimal invasive surgical techniques had benefit for patients with liver metastases from colorectal cancer.