The superpixel segmentation has been widely applied in many computer vision and image process applications.In recent years,amount of superpixel segmentation algorithms have been proposed.However,most of the current al...The superpixel segmentation has been widely applied in many computer vision and image process applications.In recent years,amount of superpixel segmentation algorithms have been proposed.However,most of the current algorithms are designed for natural images with little noise corrupted.In order to apply the superpixel algorithms to hyperspectral images which are always seriously polluted by noise,we propose a noiseresistant superpixel segmentation(NRSS)algorithm in this paper.In the proposed NRSS,the spectral signatures are first transformed into frequency domain to enhance the noise robustness;then the two widely spectral similarity measures-spectral angle mapper(SAM)and spectral information divergence(SID)are combined to enhance the discriminability of the spectral similarity;finally,the superpixels are generated with the proposed frequency-based spectral similarity.Both qualitative and quantitative experimental results demonstrate the effectiveness of the proposed superpixel segmentation algorithm when dealing with hyperspectral images with various noise levels.Moreover,the proposed NRSS is compared with the most widely used superpixel segmentation algorithm-simple linear iterative clustering(SLIC),where the comparison results prove the superiority of the proposed superpixel segmentation algorithm.展开更多
Recently,a weighted fractional Fourier transform(WFRFT)based hybrid carrier(HC)system has been proposed,which can converge single-carrier(SC)and multi-carrier(MC)systems.The cost and power dissipation of analog compon...Recently,a weighted fractional Fourier transform(WFRFT)based hybrid carrier(HC)system has been proposed,which can converge single-carrier(SC)and multi-carrier(MC)systems.The cost and power dissipation of analog components often dominate in practical HC systems.Therefore,in this paper,we analyze the baseband HC signal characteristics,including average signal power,power spectral density(PSD),probability density function(PDF),peak-to-average power ratio(PAPR),and complementary cumulative distribution function(CCDF),using a continuous-time HC signal approximation method.Through theoretical analysis and simulation validation,it is proved that the approximation method does not change the average signal power,bandwidth and out-of-band emission(OOBE).The theoretical PDF expression of HC signal with the approximation method is then proposed.Furt her more,the PDF can also explain why the PAPR of baseband continuous-time HC signal is higher than that of discrete-time HC signal.The PAPR performance and the power amplifier(PA)efficiency of HC systems in different conditions are analyzed.Through the PDF analysis of HC signal envelope and the numerical computations of PAPR.it is shown that the approximation method can offer a precise characteristic description for HC signal,which can help to improve the system PAPR performance and the PA efficiency.展开更多
针对水下目标定位中存在的传统短时傅里叶变换(Short Time Fourier Transform,STFT)方法的局限性,提出一种基于自适应窗函数的优化方法。通过研究基于谱分析的水下目标定位基本原理,聚焦于STFT的Doppler频移分析方法,并引入自适应窗函...针对水下目标定位中存在的传统短时傅里叶变换(Short Time Fourier Transform,STFT)方法的局限性,提出一种基于自适应窗函数的优化方法。通过研究基于谱分析的水下目标定位基本原理,聚焦于STFT的Doppler频移分析方法,并引入自适应窗函数进行优化,同时使用公开数据集对两种方法进行比较分析。实验结果表明,所提方法在速度估计精度和目标定位精度方面均优于传统STFT方法。展开更多
基金This work was supported in part by the National Natural Science Foundation of China under Grant No.61801222 and No.61501522in part by the Project of Shandong Province Higher Educational Science and Technology Program under Grant No.KJ2018BAN047.
文摘The superpixel segmentation has been widely applied in many computer vision and image process applications.In recent years,amount of superpixel segmentation algorithms have been proposed.However,most of the current algorithms are designed for natural images with little noise corrupted.In order to apply the superpixel algorithms to hyperspectral images which are always seriously polluted by noise,we propose a noiseresistant superpixel segmentation(NRSS)algorithm in this paper.In the proposed NRSS,the spectral signatures are first transformed into frequency domain to enhance the noise robustness;then the two widely spectral similarity measures-spectral angle mapper(SAM)and spectral information divergence(SID)are combined to enhance the discriminability of the spectral similarity;finally,the superpixels are generated with the proposed frequency-based spectral similarity.Both qualitative and quantitative experimental results demonstrate the effectiveness of the proposed superpixel segmentation algorithm when dealing with hyperspectral images with various noise levels.Moreover,the proposed NRSS is compared with the most widely used superpixel segmentation algorithm-simple linear iterative clustering(SLIC),where the comparison results prove the superiority of the proposed superpixel segmentation algorithm.
基金the National Natural Science Foundation of China(No.61671179)the National Basic Research Program of China(No.2013CB329003)the Funding of Science and Technology on Communication Networks Laboratory。
文摘Recently,a weighted fractional Fourier transform(WFRFT)based hybrid carrier(HC)system has been proposed,which can converge single-carrier(SC)and multi-carrier(MC)systems.The cost and power dissipation of analog components often dominate in practical HC systems.Therefore,in this paper,we analyze the baseband HC signal characteristics,including average signal power,power spectral density(PSD),probability density function(PDF),peak-to-average power ratio(PAPR),and complementary cumulative distribution function(CCDF),using a continuous-time HC signal approximation method.Through theoretical analysis and simulation validation,it is proved that the approximation method does not change the average signal power,bandwidth and out-of-band emission(OOBE).The theoretical PDF expression of HC signal with the approximation method is then proposed.Furt her more,the PDF can also explain why the PAPR of baseband continuous-time HC signal is higher than that of discrete-time HC signal.The PAPR performance and the power amplifier(PA)efficiency of HC systems in different conditions are analyzed.Through the PDF analysis of HC signal envelope and the numerical computations of PAPR.it is shown that the approximation method can offer a precise characteristic description for HC signal,which can help to improve the system PAPR performance and the PA efficiency.
文摘针对水下目标定位中存在的传统短时傅里叶变换(Short Time Fourier Transform,STFT)方法的局限性,提出一种基于自适应窗函数的优化方法。通过研究基于谱分析的水下目标定位基本原理,聚焦于STFT的Doppler频移分析方法,并引入自适应窗函数进行优化,同时使用公开数据集对两种方法进行比较分析。实验结果表明,所提方法在速度估计精度和目标定位精度方面均优于传统STFT方法。
