Given L, N, M ∈ N and an NZ-periodic set S in Z, let l2(S) be the closed subspace of l2(Z) consisting of sequences vanishing outside S. For f = { fl : 0≤l≤L-1 }l2(Z), we denote by G(f, N, M) the Gabor system genera...Given L, N, M ∈ N and an NZ-periodic set S in Z, let l2(S) be the closed subspace of l2(Z) consisting of sequences vanishing outside S. For f = { fl : 0≤l≤L-1 }l2(Z), we denote by G(f, N, M) the Gabor system generated by f, and by L(f, N, M) the closed linear subspace generated by G(f, N, M). This paper addresses density results, frame conditions for a Gabor system G(g, N, M) in l2(S), and Gabor duals of the form G(a, N, M) in some L(h, N, M) for a frame G(g, N, M) in l2(S) (so-called oblique duals). We obtain a density theorem for a Gabor system G(g, N, M) in l2(S), and show that such condition is suficient for theexistence of g={XE1:0≤l≤L-1} with G(g,N,m) We characterize g with G(g,N,m) being respectively a frame for L(g,N,m) being a tight frame for l2(S).and G(h, N, M ) in L(h, N, M ), we establish a criterion for the existence of an oblique Gabor dual of g in L(h, N, M), study the uniqueness of oblique Gabor dual, and derive an explicit expression of a class of oblique Gabor duals (among which the one with the smallest norm is obtained). Some examples are also provided.展开更多
针对胸部CT(Computed Tomography)DICOM(Digital Imaging and Communication of Medicine)图像中多窗显示时,需要对胸部各组织进行分割的问题,本文根据各组织的CT值范围,结合贴标签算法实现多组织分割.首先根据CT成像原理,不同组织具有...针对胸部CT(Computed Tomography)DICOM(Digital Imaging and Communication of Medicine)图像中多窗显示时,需要对胸部各组织进行分割的问题,本文根据各组织的CT值范围,结合贴标签算法实现多组织分割.首先根据CT成像原理,不同组织具有稳定的CT值范围,将图像初步分割为肺、肌肉、骨和皮肤区域.然后依据组织的面积特征,应用贴标签算法去除噪声.不同厂家成像系统,不同年龄、性别患者图像的分割结果表明,本文方法都能正确分割出肺、肌肉、骨和皮肤区域.展开更多
For many water quality studies,a data analyst,or modeler, may need to know the spatio-temproal patterns of the data sets and their relationships in both pre-processing and post-processing. Geographic Information Syste...For many water quality studies,a data analyst,or modeler, may need to know the spatio-temproal patterns of the data sets and their relationships in both pre-processing and post-processing. Geographic Information System(GIS) can provide an exploratory spat展开更多
Aiming at the poor performance of speech signal detection at low signal-to-noise ratio(SNR),a method is proposed to detect active speech frames based on multi-window time-frequency(T-F)diagrams.First,the T-F diagram o...Aiming at the poor performance of speech signal detection at low signal-to-noise ratio(SNR),a method is proposed to detect active speech frames based on multi-window time-frequency(T-F)diagrams.First,the T-F diagram of the signal is calculated based on a multi-window T-F analysis,and a speech test statistic is constructed based on the characteristic difference between the signal and background noise.Second,the dynamic double-threshold processing is used for preliminary detection,and then the global double-threshold value is obtained using K-means clustering.Finally,the detection results are obtained by sequential decision.The experimental results show that the overall performance of the method is better than that of traditional methods under various SNR conditions and background noises.This method also has the advantages of low complexity,strong robustness,and adaptability to multi-national languages.展开更多
基金supported by National Natural Science Foundation of China (Grant Nos. 10901013, 10671008)Beijing Natural Science Foundation (Grant No. 1092001)+1 种基金the Scientific Research Common Program of Beijing Municipal Commission of Education (Grant No. KM201110005030)the Project Sponsored by SRF for ROCS, SEM of China
文摘Given L, N, M ∈ N and an NZ-periodic set S in Z, let l2(S) be the closed subspace of l2(Z) consisting of sequences vanishing outside S. For f = { fl : 0≤l≤L-1 }l2(Z), we denote by G(f, N, M) the Gabor system generated by f, and by L(f, N, M) the closed linear subspace generated by G(f, N, M). This paper addresses density results, frame conditions for a Gabor system G(g, N, M) in l2(S), and Gabor duals of the form G(a, N, M) in some L(h, N, M) for a frame G(g, N, M) in l2(S) (so-called oblique duals). We obtain a density theorem for a Gabor system G(g, N, M) in l2(S), and show that such condition is suficient for theexistence of g={XE1:0≤l≤L-1} with G(g,N,m) We characterize g with G(g,N,m) being respectively a frame for L(g,N,m) being a tight frame for l2(S).and G(h, N, M ) in L(h, N, M ), we establish a criterion for the existence of an oblique Gabor dual of g in L(h, N, M), study the uniqueness of oblique Gabor dual, and derive an explicit expression of a class of oblique Gabor duals (among which the one with the smallest norm is obtained). Some examples are also provided.
文摘针对胸部CT(Computed Tomography)DICOM(Digital Imaging and Communication of Medicine)图像中多窗显示时,需要对胸部各组织进行分割的问题,本文根据各组织的CT值范围,结合贴标签算法实现多组织分割.首先根据CT成像原理,不同组织具有稳定的CT值范围,将图像初步分割为肺、肌肉、骨和皮肤区域.然后依据组织的面积特征,应用贴标签算法去除噪声.不同厂家成像系统,不同年龄、性别患者图像的分割结果表明,本文方法都能正确分割出肺、肌肉、骨和皮肤区域.
文摘For many water quality studies,a data analyst,or modeler, may need to know the spatio-temproal patterns of the data sets and their relationships in both pre-processing and post-processing. Geographic Information System(GIS) can provide an exploratory spat
基金The National Natural Science Foundation of China(No.12174053,91938203,11674057,11874109)the Fundamental Research Funds for the Central Universities(No.2242021k30019).
文摘Aiming at the poor performance of speech signal detection at low signal-to-noise ratio(SNR),a method is proposed to detect active speech frames based on multi-window time-frequency(T-F)diagrams.First,the T-F diagram of the signal is calculated based on a multi-window T-F analysis,and a speech test statistic is constructed based on the characteristic difference between the signal and background noise.Second,the dynamic double-threshold processing is used for preliminary detection,and then the global double-threshold value is obtained using K-means clustering.Finally,the detection results are obtained by sequential decision.The experimental results show that the overall performance of the method is better than that of traditional methods under various SNR conditions and background noises.This method also has the advantages of low complexity,strong robustness,and adaptability to multi-national languages.
