一种从辐射噪声中提取调制谱的方法

在水下航行器的辐射噪声中,螺旋桨节拍对航行器的宽带辐射噪声存在着明显的振幅调制,调制频率与航行器螺旋桨的转速有关。该特征可用于估计航行器的速度及目标分类与识别。本文利用子波变换原理,从实测的航行器辐射噪声中提取了它的调制谱,并据此对螺旋桨转速进行了估计,计算机仿真结果与实测的螺旋桨的转速具有良好的一致性。     

Application of cogwheel phase cycling to sideband manipulation experiments in solid-state NMR

Cogwheel phase-cycling schemes are applied to sideband suppression and sideband separation experiments in solid-state NMR. It is shown that cogwheel phase cycles lead to the elimination of most pulse imperfection effects, while using far fewer experimental signal acquisitions than conventional phase-cycling methods.     

基于波前像差的视网膜空间像调制度测定

提出了一种计算复色光下人眼视网膜空间像调制度的方法.利用Hartmann-Shack波前传感器测量的波前像差数据，求得眼睛光学系统的调制传递函数；利用CSV-1000测试仪和VAF-1000视锐度测试仪分别测量同一只眼睛的全眼对比敏感度函数以及视锐度，由调制传递函数、对比敏感度函数以及视锐度之间的关联获得复色光下人眼视网膜空间像调制度曲线.结果表明：视网膜空间像调制度曲线与眼光学系统的调制传递函数无关，并且正常人眼（无视网膜疾病）的视网膜空间像调制度值相近.因此多眼的空间像调制度曲线的统计平均值可以作为标准，用来评判人眼视网膜及视神经疾病.     

Generation, detection and characterization of optical minimum shift keying data format

This paper presents the detailed principle on the generation and detection of optical minimum shift keying (MSK) format for high-speed and high spectral efficiency WDM systems. 10.7 Gb/s optical MSK data is successfully generated by experiment using the proposed scheme. The results show that optical MSK signal exhibits very compact optical spectrum, which is promising for high spectral efficiency WDM applications. Simulation results on dispersion and nonlinear tolerance comparison confirm that MSK signal has better dispersion tolerance and nonlinear tolerance compared with 50% duty cycle return-to-zero differential phase shift keying (RZ-DPSK) and 50% duty cycle RZ on-off-keying (RZ-OOK) formats.     

Application of moiré technique to the measurement of modulation transfer functions (MTF) of printing systems

It is shown theoretically and verified experimentally that by writing a low spatial frequency Ronchi grating by a computer and printing two copies of it on two transparencies by a printer, the modulation transfer function (MTF) of the printed image can be evaluated by measuring the transmittance of the superimposed gratings in a moiré fringe spacing. Application of the technique is quite simple and the results are reasonably reproducible. The technique does not require a high sensitive intensity detector and a very narrow slit for transmission scanning. Also, the presented technique can be applied to other imaging systems.     

Determination of the limit of photon mass and cosmic magnetic vector with rotating torsion balance

A rotating torsion balance method to detect the product of the photon mass squared and the ambient cosmic vector potential is proposed. This modulation method is efficacious whether the vector potential is fortuitously aligned with Earth's rotation axis or not, and the experimental precision of the modulation method can be improved by at least an order of magnitude compared to the statistical method.     

Spontaneous 2D modulation instability in second harmonic generation process

Two-dimensional modulation instability (2DMI) is experimentally demonstrated in a classical second harmonic generation setup. The spatial spectrum is measured and reveals typical 2DMI bands, in agreement with the analytical MI model. These observations are confirmed by (2 + 1)D numerical simulations.     

A flexible fast 3D profilometry based on modulation measurement

This paper proposes a flexible fast profilometry based on modulation measurement. Two orthogonal gratings through a beam splitter are vertically projected on an object surface, and the measured object is placed between the imaging planes of the two gratings. Then the image of the object surface modulated by the orthogonal gratings can be obtained by a CCD camera in the same direction as the grating projection. This image is processed by the operations consisting of performing the Fourier transform, spatial frequency filtering and inverse Fourier transform. Using the modulation distributions of two grating patterns, we can reconstruct the 3D shape of the object. In the measurement process, we only need to capture one fringe pattern, so it is faster than the MMP and remains the advantages of it. In the article, the principle of this method, the setup of the measurement system, some simulations and primary experiment results are given. The simulative and experimental result proves it can restore the 3D shape of the complex object fast and comparatively accurate. Because only one fringe pattern is needed in the testing, our method has a promising extensive application prospect in real-time acquiring and dynamic measurement of 3D data of complex objects.     

Akhmediev breather evolution in optical fiber for realistic initial conditions

We study numerically Akhmediev breather dynamics in optical fibers under initial conditions that do not correspond to an ideal infinitesimal modulation on a plane wave. We examine two modifications that are commonly encountered in realistic experiments: (i) a finite-amplitude (not necessarily weak) initial modulation; (ii) the use of pulsed excitation. In the first case, we derive an expression for the propagation distance required to generate a train of compressed breather pulses. In the second case, we show that breather dynamics with pulsed excitation can be interpreted in terms of local breather states at different points on the pulse envelope.