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1.
Whispered speech enhancement using auditory masking model in modified Meldomain and Speech Absence Probability(SAP)was proposed.In light of the phonation characteristic of whisper,we modify the Mel-frequency Scaling model.Whispered speech is filtered by the proposed model.Meanwhile,the value of masking threshold for each frequency band is dynamically determined by speech absence probability.Then whispered speech enhancement is conducted by adaptively rectifying the spectrum subtraction coefficients using different masking threshold values.Results of objective and subjective tests on the enhanced whispered signal show that compared with other methods;the proposed method can enhance whispered signal with better subjective auditory quality and less distortion by reducing the music noise and background noise under the masking threshold value.  相似文献   

2.
Multicolor manipulation of negative refraction in a three-level Λ atomic system is theoretically investigated. Based on multicolor coherence, the negative refractive index can be obtained with reduced absorption. The refractive index can also be controlled by changing the sum of the phases of the sidebands in the trichromatic driving fields. By adjusting the sum phase, the refractive index can be varied between negative and positive in two different frequency bands. Furthermore, the frequency band corresponding to the negative refractive index is widened by increasing the intensity and the frequency difference of the trichromatic field.  相似文献   

3.
Assisted by multipartite entanglement, Quantum information may be split so that the original qubit can be reconstructed if and only if the recipients cooperate. This paper proposes an experimentally feasible scheme for splitting quantum information via W-type entangled states in cavity QED systems, where three-level Rydberg atoms interact with nonresonant cavities. Since W-type states are used as the quantum channel and the cavities are only virtually excited, the scheme is easy to implement and robust against decoherence, and the dependence on the quality factor of the cavities is greatly reduced.  相似文献   

4.
Grouped pair-wise comparison for subjective sound quality evaluation   总被引:2,自引:0,他引:2  
In subjective sound quality pair-wise comparison evaluation, test time grows with square of the number of sound stimulus. For this reason, subjective evaluation of large quantity of stimulus is difficult to carry out with pair-wise comparison method. A grouped pair-wise comparison (GPC) method is proposed to greatly decrease time and difficult of subjective comparison test, in which stimuli in the whole evaluation corpus are divided into N test groups, with reference-link stimuli configured in each group. Derived from subjective results of each group, final results of all stimuli are reconstructed, and their perceptual attributes of sound quality can be analyzed. With car interior noise as example, realization of subjective sound quality evaluation with GPC method is introduced. The results of GPC evaluation are in good agreement with those obtained from paired comparison and semantic differential methods.  相似文献   

5.
Stripe motion artifacts caused by phase fluctuation in phase-resolved optical coherence tomography (OCT) result in the quality degradation of the image of in vivo blood flow of human eye. In order to suppress the stripe motion artifacts, we design a kind of frequency rejection filter aimed at the frequency spectrum characteristics of the image. Blood flow images of human eye acquired by our research group and another group are filtered to show the performance of the proposed method. Experimental results indicate that the stripe motion artifacts in the projection images are rejected significantly with minimal loss of signal information. The proposed filter can also be used in other imaging systems with similar stripe noise.  相似文献   

6.
An evaluation for objectively assessing the target detectability in night vision color fusion images is proposed.On the assumption that target detectability could be modeled as the perceptual color variation between the target and its optimal sensitive background region,we propose an objective target detectability metric in CIELAB color space defined by four color information features:target luminance,region perceptual luminance variation in human vision system,region hue difference,and region chroma difference.Experimental results show that this proposed metric is perceptually meaningful because it corresponds well with subjective evaluation.  相似文献   

7.
The frequency down-conversion of one-dimensional photonic crystals with the coupled cavity structure is investigated by the nonlinear finite-difference time-domain method. The efficient frequency conversion is obtained by utilizing the advantages of the broad eigenfrequency band, the strong localization and the Bloch phase matching of the coupled cavity structure. More importantly, the signal frequency could be tuned continuously within the whole band of the coupled cavity structure (with a bandwidth to central frequency ratio of 5.4%), and the gains are homogeneous in the band.  相似文献   

8.
We propose a method to directly measure phase-related noise characteristics of single-frequency lasers in the 728–980 nm band based on a 120°phase difference interferometer.Differential phase information of the laser under test is demodulated via the interferometer.Other parameters related to the phase noise characteristics such as linewidth at different observation time, phase/frequency noise, power spectrum density of phase/frequency fluctuation, and Allan deviation are further obtained.Frequency noise as low as 1 Hz~2/Hz can be measured using our system.Then the phase-related noise characteristics of two commercial lasers frequently used in cold atomic clocks are studied systematically by the method.Furthermore, several influencing factors and their relative evolution laws are also revealed, such as the pump current and frequency-locking control parameters.This would help to optimize the laser performance, select laser sources, and evaluate the system performance for cold atomic physics applications.  相似文献   

9.
In synthetic transmit aperture medical ultrasound imaging field,a compressed sensing ultrasound imaging method based on the sparsity in frequency domain is presented in order to reduce huge amount of data and large numbers of receiving channels.First,the sparsity in frequency domain is verified.Then the echo signal is compressively sampled in time-spatial domain based on compressed sensing and the echo signal is reconstructed by solving an optimization problem.Finally the image is made by using the synthetic transmit aperture approach.The experiments based on point target and fetus target are used to verify the proposed method.The MSE,resolution and image quality of reconstructed image and those of original image are compared and analyzed.The results show that only 30%amount of data and 50%of receiving channels were used to implement ultrasound imaging without reducing the quality of image in experiment.The amount of data and the complexity of system are reduced greatly by the proposed method based on compressed sensing.  相似文献   

10.
史力斌  康莉  金健维  迟锋 《中国物理 B》2009,18(10):4418-4424
In the paper, density of states, band structure and electron density difference of Zn1-xCdxO are calculated by first principles, here x varies from 0 to 0.75 at intervals of 0.125, and the band gap obtained from band structure changes from 0.968 eV to 0.043 eV. The lattice strain and p-d repulsion theory are used to investigate variation of the band gap, the results obtained show that the variation is mainly due to the lattice tensile strain. The p-d repulsion in Zn1-xCdxO cannot be neglected. In addition, electron density difference can be used to verify the results.  相似文献   

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