To improve localization accuracy, the spherical microphone arrays are used to capture high-order wavefield in- formation. For the far field sound sources, the array signal model is constructed based on plane wave deco...To improve localization accuracy, the spherical microphone arrays are used to capture high-order wavefield in- formation. For the far field sound sources, the array signal model is constructed based on plane wave decomposition. The spatial spectrum function is calculated by minimum variance distortionless response （MVDR） to scan the three-dimensional space. The peak values of the spectrum function correspond to the directions of multiple sound sources. A diagonal loading method is adopted to solve the ill-conditioned cross spectrum matrix of the received signals. The loading level depends on the alleviation of the ill-condition of the matrix and the accuracy of the inverse calculation. Compared with plane wave decomposition method, our proposed localization algorithm can acquire high spatial resolution and better estimation for multiple sound source directions, especially in low signal to noise ratio （SNR）.展开更多
The noncontact blade tip timing(BTT)measurement has been an attractive technology for blade health monitoring(BHM).However,the severe undersampled BTT signal causes a significant challenge for blade vibration paramete...The noncontact blade tip timing(BTT)measurement has been an attractive technology for blade health monitoring(BHM).However,the severe undersampled BTT signal causes a significant challenge for blade vibration parameter identification and fault feature extraction.This study proposes a novel method based on the minimum variance distortionless response(MVDR)of the direction of arrival(DoA)estimation for blade natural frequency estimation from the non-uniformly undersampled BTT signals.First,based on the similarity between the general data acquisition model for BTT and the antenna array model in DoA estimation,the circumferentially arranged probes on the casing can be regarded as a non-uniform linear array.Thus,BTT signal reconstruction is converted into the DoA estimation problem of the non-uniform linear array signal.Second,MVDR is employed to address the severe undersampling issue and recover the BTT undersampled signal.In particular,spatial smoothing is innovatively utilized to enhance the estimation of covariance matrix of the BTT signal to avoid ill-condition or singularity,while improving efficiency and robustness.Lastly,numerical simulation and experimental testing are employed to verify the validity of the proposed method.Monte Carlo simulation results suggest that the proposed method behaves better than conventional methods,especially under a lower signal-to-noise ratio condition.Experimental results indicate that the proposed method can effectively overcome the severe undersampling problem of BTT signal induced by physical limitations,and has a strong potential in the field of BHM.展开更多
目标方位估计(Direction of arrival,DOA)和信号恢复分别是水下目标定位、跟踪与识别的前提.基于盲源分离方法可以得到含有阵列流形信息的解混矩阵,融合成熟的高分辨方法提出了一种新的方位估计、信号恢复模型和方法.在宽带信号背景下...目标方位估计(Direction of arrival,DOA)和信号恢复分别是水下目标定位、跟踪与识别的前提.基于盲源分离方法可以得到含有阵列流形信息的解混矩阵,融合成熟的高分辨方法提出了一种新的方位估计、信号恢复模型和方法.在宽带信号背景下进行了仿真实验,结果表明该方法可实现目标方位的实时估计和目标信号的恢复.在同等条件下完成同样的目标方位分辨率,比单纯的高分辨方法要求的阵元数和快拍数较少,要求的信噪比要低.海上实测数据检验也表明,比常规的最小方差无失真响应(Minimum variance distortionless response,MVDR)方法得到了更好的结果,明显提高了弱目标信号的空间谱能量,增强了检测弱目标信号的能力.展开更多
对新疆低温煤焦油抽提得到的酸性组分、碱性组分、中性组分及柱分离中性组分得到的不同极性组分进行1 H NMR和13 C NMR表征,同时利用无畸变极化转移增益法对不同类型的碳进行了归属。结果表明,新疆低温煤焦油是一种结构复杂的化合物,其...对新疆低温煤焦油抽提得到的酸性组分、碱性组分、中性组分及柱分离中性组分得到的不同极性组分进行1 H NMR和13 C NMR表征,同时利用无畸变极化转移增益法对不同类型的碳进行了归属。结果表明,新疆低温煤焦油是一种结构复杂的化合物,其中含有大量的亚甲基碳、次甲基碳等油潜力碳,可加工成汽油、柴油等高附加值的燃料油;酸性组分中含有大量的酚基,可提取酚类化工原料;中性组分以多烷基芳烃化合物为主,可用于生产芳烃等有机化合物。低温煤焦油是一种有价值的化工原料,同时,高分辨NMR为低温煤焦油的结构研究提供了一种可靠的表征手段,具有一定的研究意义。展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No.61001160)the Doctoral Foundation of Ministry of Education (Grant No.20093108120018)the Shanghai Leading Academic Discipline Project (Grant No.S30108)
文摘To improve localization accuracy, the spherical microphone arrays are used to capture high-order wavefield in- formation. For the far field sound sources, the array signal model is constructed based on plane wave decomposition. The spatial spectrum function is calculated by minimum variance distortionless response （MVDR） to scan the three-dimensional space. The peak values of the spectrum function correspond to the directions of multiple sound sources. A diagonal loading method is adopted to solve the ill-conditioned cross spectrum matrix of the received signals. The loading level depends on the alleviation of the ill-condition of the matrix and the accuracy of the inverse calculation. Compared with plane wave decomposition method, our proposed localization algorithm can acquire high spatial resolution and better estimation for multiple sound source directions, especially in low signal to noise ratio （SNR）.
基金the National Natural Science Foundation of China(Grant Nos.52105117 and 51875433)the Funds for Distinguished Young Talent of Shaanxi Province,China(Grant No.2019JC-04).
文摘The noncontact blade tip timing(BTT)measurement has been an attractive technology for blade health monitoring(BHM).However,the severe undersampled BTT signal causes a significant challenge for blade vibration parameter identification and fault feature extraction.This study proposes a novel method based on the minimum variance distortionless response(MVDR)of the direction of arrival(DoA)estimation for blade natural frequency estimation from the non-uniformly undersampled BTT signals.First,based on the similarity between the general data acquisition model for BTT and the antenna array model in DoA estimation,the circumferentially arranged probes on the casing can be regarded as a non-uniform linear array.Thus,BTT signal reconstruction is converted into the DoA estimation problem of the non-uniform linear array signal.Second,MVDR is employed to address the severe undersampling issue and recover the BTT undersampled signal.In particular,spatial smoothing is innovatively utilized to enhance the estimation of covariance matrix of the BTT signal to avoid ill-condition or singularity,while improving efficiency and robustness.Lastly,numerical simulation and experimental testing are employed to verify the validity of the proposed method.Monte Carlo simulation results suggest that the proposed method behaves better than conventional methods,especially under a lower signal-to-noise ratio condition.Experimental results indicate that the proposed method can effectively overcome the severe undersampling problem of BTT signal induced by physical limitations,and has a strong potential in the field of BHM.
文摘对新疆低温煤焦油抽提得到的酸性组分、碱性组分、中性组分及柱分离中性组分得到的不同极性组分进行1 H NMR和13 C NMR表征,同时利用无畸变极化转移增益法对不同类型的碳进行了归属。结果表明,新疆低温煤焦油是一种结构复杂的化合物,其中含有大量的亚甲基碳、次甲基碳等油潜力碳,可加工成汽油、柴油等高附加值的燃料油;酸性组分中含有大量的酚基,可提取酚类化工原料;中性组分以多烷基芳烃化合物为主,可用于生产芳烃等有机化合物。低温煤焦油是一种有价值的化工原料,同时,高分辨NMR为低温煤焦油的结构研究提供了一种可靠的表征手段,具有一定的研究意义。
