全电视信号PCM编码色度副载波量化噪声的讨论

分析了全电视信号ＰＣＭ编码色度副载波量化噪声，并讨论了量化噪声与取样频率ｆｓ和量化比特数ｎ的关系。

小波域自适应图像水印算法研究

该文提出一种在小波域内自适应于图像内容的数字水印方案.算法利用图像系数的零树结构,自适应地确定被嵌水印序列的长度,并根据小波域的量化噪声自适应地确定水印的嵌入强度,保证了水印序列的能量小于图像可容纳的噪声上限,使水印图像同时具有良好的视觉效果和鲁棒性.在检测端可根据水印图像的统计特性确定水印的检测阈值,不需要参考原图就能判断水印是否存在.对水印图像的攻击实验表明该算法对噪声干扰及常见的图像处理技术具有较好的鲁棒性.

Analysis of SNR for Acoustic Vector Sensor Linear Array in Volume and Surface-generated Noise Fields

Acoustic vector sensor consists of pressure and particle velocity sensors,which measure the three-dimensional acoustic particle velocity,as well as the pressure at one location at the same time.By preserving the amplitude and phase information of the pressure and particle velocity,they possess a number of advantages over traditional scalar sensors.Signal-to-noise ratio (SNR) gain (which is often called array gain) is one of such advantages and is always interested by all of us.But it is not unchangeable if the spatial correlation of the noise field varies.Much more important,it is difficult to be given if the noise becomes complex.In this paper,spatial correlation of the vector field of isotropic volume-noise and surface-generated noise has been introduced briefly.Based on the results,the combined SNR output of a vector linear array is investigated and the maximum gain is given in the specified noise.Computer simulation shows that the output of one array in the same noise is not the same in different gestures.And then we find the best gesture through SNR calculation and obtain the biggest gain,which has important meaning to guide how to deploy an array in practice.We also should use the array with respect to the characteristics of the real ambient noise,especially in anisotropic noise field.

A continuous differentiable wavelet threshold function for speech enhancement

Enhanced speech based on the traditional wavelet threshold function had auditory oscillation distortion and the low signal-to-noise ratio (SNR). In order to solve these problems, a new continuous differentiable threshold function for speech enhancement was presented. Firstly, the function adopted narrow threshold areas, preserved the smaller signal speech, and improved the speech quality; secondly, based on the properties of the continuous differentiable and non-fixed deviation, each area function was attained gradually by using the method of mathematical derivation. It ensured that enhanced speech was continuous and smooth; it removed the auditory oscillation distortion; finally, combined with the Bark wavelet packets, it further improved human auditory perception. Experimental results show that the segmental SNR and PESQ (perceptual evaluation of speech quality) of the enhanced speech using this method increase effectively, compared with the existing speech enhancement algorithms based on wavelet threshold.

An improved joint method for onset picking of acoustic emission signals with noise

The onset times of acoustic signals with spikes,heavy bodies and unclear takeoffs are difficult to be picked accurately by the automatic method at present.To deal with this problem,an improved joint method based on the discrete wavelet transform(DWT),modified energy ratio(MER)and Akaike information criterion(AIC)pickers,has been proposed in this study.First,the DWT is used to decompose the signal into various components.Then,the joint application of MER and AIC pickers is carried out to pick the initial onset times of all selected components,where the minimum AIC position ahead of MER onset time is regarded as the initial onset time.Last,the average for initial onset times of all selected components is calculated as the final onset time of this signal.This improved joint method is tested and validated by the acoustic signals with different signal to noise ratios(SNRs)and waveforms.The results show that the improved joint method is not affected by the variations of SNR,and the onset times picked by this method are always accurate in different SNRs.Moreover,the onset times of all acoustic signals with spikes,heavy bodies and unclear takeoffs can be accurately picked by the improved joint method.Compared to some other methods including MER,AIC,DWT-MER and DWT-AIC,the improved joint method has better SNR stabilities and waveform adaptabilities.

Entanglement Dynamics of Two-Qubit System in Different Types of Noisy Channels

In this paper, we study entanglement dynamics of a two-qubit extended Werner-like state locally, interacting with independent noisy channels, i.e., amplitude damping, phase damping, and depolarizing channels. We show that the purity of initial entangled state has direct impacts on the entanglement robustness in each noisy channel. That is, if the initial entangled state is prepared in mixed instead of pure form, the state may exhibit entanglement sudden death （ESD） and/or be decreased for the critical probability at which the entanglement disappear.

The Representation of a Broadband Vector Field

Compared to a scalar pressure sensor, a vector sensor can provide a higher signal-to-noise ratio （SNR） signal and more detailed intbrmation on the sound field. Study on vector sensors and their applications have become a hot topic. Research on the representation of a vector field is highly relevant for extending the scope of vector sensor technology. This paper discusses the range-frequency distribution of the vector field due to a broadband acoustic source moving in a shallow-water waveguide as the self noise of a surface ship, and the vector extension of the waveguide impulse response measured over a limited frequency range using an active source of known waveform. From theory analysis and numerical simulation, the range-frequency representation of a vector field exhibits an interference structure qualitatively similar to that of the corresponding pressure field but, being quantitatively different, provides additional information on the waveguide, especially through the vertical component. For the range-frequency representation, physical quantities that can better exhibit the interference characteristics of the wavegaide are the products of pressure and particle velocity and of the pressure and pressure gradient. An image processing method to effectively detect and isolate the individual striations from an interference structure was reviewed briefly. The representation of the vector impulse response was discussed according to two different measurement systems, also known as particle velocity and pressure gradient. The vector impulse response representation can not only provide additional information from pressure only but even more than that of the range-frequency representation.

Quantum Secret Sharing with Error Correction

We investigate in this work a quantum error correction on a five-qubits graph state used for secret sharing through five noisy channels. We describe the procedure for the five, seven and nine qubits codes. It is known that the three codes always allow error recovery if only one among the sent qubits is disturbed in the transmitting channel. However, if two qubits and more are disturbed, then the correction will depend on the used code. We compare in this paper the three codes by computing the average fidelity between the sent secret and that measured by the receivers. We will treat the case where, at most, two qubits are affected in each one of five depolarizing channels.

Fault tolerant two-step quantum secure direct communication protocol against collective noises

This work proposes two fault tolerant quantum secure direct communication （QSDC） protocols which are robust against two kinds of collective noises： the collective-dephasing noises and the collective-rotation noises, respectively. The two QSDC protocols are constructed from four-qubit DF states which consist of two logical qubits. The receiver simply performs two Bell state measurements （rather than four-qubit joint measurements） to obtain the secret message. The protocols have qubit efficiency twice that of the other corresponding fault tolerant QSDC protocols. Furthermore, the proposed protocols are free from Trojan horse attacks.

Effects of noisy quantum channels on one-qubit rotation gate

We investigate the effects of noisy quantum channels on the entanglement of cluster states and one way quantum computational gates.We take a basic model,the rotational gate about x axis based on the cluster state,in order to get the most essential effects of the paradigmatic noisy quantum channels.The entanglement of cluster states in the noisy channels and the fidelity between the rotated state without noisy channel and that with noisy channel are calculated.

Probabilistic multiparty-controlled teleportation of an arbitrary m-qubit state with a pure entangled quantum channel against collective noise

We present two general schemes for multiparty-controlled teleportation of an arbitrary m-qubit state against two types of collective noise by using m pure entangled states as the quantum channel.The first is used to control teleporting for an arbitrary m-qubit state against a collective-dephasing noise with nonmaximally entangled quantum channel,and the second is in teleporting the m-qubit state against the collective-rotation noise.The receiver can reconstruct the original state with an auxiliary qubit and the corresponding unitary operations if he cooperates with all the controllers.The scheme is optimal as the probability that the receiver reconstructs the original state equals to the entanglement of the quantum channel.

Quantum Measurement of Two-Qubit System in Damping Noise Environment

It is known that the inevitable interaction of the entangled qubits with their environments may result in the degradation of quantum correlation.We study the decoherence of two remote qubits under general local single-and two-sided amplitude-damping channel(ADC).By using concurrence,quantum discord and Clauser-Horne-ShimonyHolt(CHSH)inequality,we find that the relation between the residual quantum correlations and the initial ones are different.Recently,Wang et al.[Int.J.Theor.Phys.54(2015)5]showed that there exist a set of partially entangled states that are more robust than maximally entangled states in terms of the residual quantum correlation measured by concurrence,fully entangled fraction and quantum discord,respectively.Here we find that both in single-and two-sided ADC,only the evolution of CHSH inequality with the initial parameter is proportional to that of the initial nonlocality.That means the initial state with maximally nonlocality will retain its role in the evolution.It implies that the evolution of nonlocality may reveal the characteristics of quantum state better.Furthermore,we discuss the evolutions of the three different quantum measurements with the initial parameter under generalized amplitude damping channel(GADC)and find that they are all proportional to that of the initial state.

Effects of Quantum Noise on Quantum Clock Synchronization

In laboratory environment, the channel apparatus will generate particular dominant quantum noise. The noise then will give rise to some errors during synchronization. In this work, the accuracies of one qubit transport protocol and entangled states transport protocol in the presence of noise have been studied. With the help of three important and familiar noise models, the quantum noise will degrade the accuracy has been proved. Due to the influence of quantum noise, the accuracy of entangled qubits decrease faster than that of one qubit. The entangled states will improve the accuracy in noise-free channel, and will degrade the accuracy in noise channel.

Robust QKD-based private database queries based on alternative sequences of single-qubit measurements

Quantum channel noise may cause the user to obtain a wrong answer and thus misunderstand the database holder for existing QKD-based quantum private query(QPQ) protocols. In addition, an outside attacker may conceal his attack by exploiting the channel noise. We propose a new, robust QPQ protocol based on four-qubit decoherence-free(DF) states. In contrast to existing QPQ protocols against channel noise, only an alternative fixed sequence of single-qubit measurements is needed by the user(Alice) to measure the received DF states. This property makes it easy to implement the proposed protocol by exploiting current technologies. Moreover, to retain the advantage of flexible database queries, we reconstruct Alice's measurement operators so that Alice needs only conditioned sequences of single-qubit measurements.

AIG Based Nonlinear Anisotropic Smoothing Strategy for Vector-Valued Images

The effects of the Rician noise on the calculated tensors are analyzed and an affine invariant gradient (AIG) based nonlinear anisotropic smoothing strategy is presented.The AIG based smoothing strategy is a development of the affine invariant nonlinear anisotropic diffusion(AINAD) restoration model,introduced by Guillermo Sapiro,and adopted to restore vector-valued data.To evaluate the efficiency of the presented AINAD model in accounting for the Rician noise introduced into the vector-valued data,the peak-to-peak signal-to-noise ratio(PSNR),signal-to-mean squared error ratio(SMSE) and Beta(parameter that stands for edge preservation) metrics are used.The experiment results acquired from the synthetic and real data prove the good performance of the presented filter.