Optomechanical-organized multipulse dynamics in ultrafast fiber laser

A novel organized multipulse pattern and its birth dynamics under strong optomechanical effect in microfiber-assisted ultrafast fiber laser are investigated in this work. The background pulses are observed to obviously exhibit selectively amplifying self-organized process of evolving into quasi-stable equidistant clusters. The radio frequency spectrum of the multipulse pattern displays a harmonic mode-locking-like behavior with a repetition rate of 2.0138 GHz, corresponding to the frequency of torsional-radial (TR_2m) acoustic mode in microfiber. The results show the evidence of optomechanical effect in dominating the birth dynamics and pattern of multipulse.     

Effect of thickness variations of lithium niobate on insulator waveguide on the frequency spectrum of spontaneous parametric down-conversion

We study the effect of waveguide thickness variations on the frequency spectrum of spontaneous parametric down-conversion in the periodically-poled lithium niobate on insulator (LNOI) waveguide. We analyze several variation models and our simulation results show that thickness variations in several nanometers can induce distinct effects on the central peak of the spectrum, such as narrowing, broadening, and splitting. We also prove that the effects of positive and negative variations can be canceled and thus lead to a variation-robust feature and an ultra-broad bandwidth. Our study may promote the development of on-chip photon sources in the LNOI platform, as well as opens up a way to engineer photon frequency state.     

Maximum cross-correlated kurtosis-based unsaturated stochastic resonance and its application to bearing fault diagnosis

Considering the random impulses of mechanical noise and the limitations involved while identifying mechanical fault impulse signals via traditional measurement indices of signal-to-noise ratio, which require the characteristic frequency to be known in advance, this study proposes an adaptive unsaturated stochastic resonance method employing maximum cross-correlated kurtosis as the signal detection index. The proposed method combines the features of a cross-correlated coefficient to indicate periodic fault transients and those of spectrum kurtosis to locate these transients in the frequency domain. Actual vibration signals collected from motor and gear bearings subjected to heavy noise are used to demonstrate the effectiveness of the proposed method. Through a coarse tree-based machine learning method, the proposed method is verified to be more suitable for explaining the periodic impulse components of bearing signals, as compared to the ensemble empirical mode decomposition denoising method and unsaturated stochastic resonance using the kurtosis-intercorrelation index.     

Double Gaussian potential stochastic resonance method and its application in centrifugal fan blade crack detection

Stochastic resonance (SR) has been extensively utilized in the field of weak fault signal detection for its characteristic of enhancing weak signals by transferring the noise energy. Aiming at solving the output saturation problem of the classical bistable stochastic resonance (CBSR) system, a double Gaussian potential stochastic resonance (DGSR) system is proposed. Moreover, the output signal-to-noise ratio (SNR) of the DGSR method is derived based on the adiabatic approximation theory to analyze the effect of system parameters on the DGSR method. At the same time, for the purpose of overcoming the drawback that the traditional SNR index needs to know the fault characteristic frequency (FCF), the weighted local signal-to-noise ratio (WLSNR) index is constructed. The DGSR with WLSNR can obtain optimal parameters adaptively, thereby establishing the DGSR system. Ultimately, a DGSR method is proposed and applied in centrifugal fan blade crack detection. Through simulations and experiments, the effectiveness and superiority of the DGSR method are verified.     

Cryptanalysis and Improvement in Multi-Party Quantum Key Distribution Protocol with New Bell States Encoding Mode

International Journal of Theoretical Physics - Ma et al. [Int. J. Theor. Phys. (2021): 1328–1338] proposed a multi-party quantum key distribution (MQKD) protocol using Bell states, in which...     

土壤质地分类的近红外光谱分析方法研究

依据所收集的25种土样,采用两种不同精度仪器、三种光谱方法以及3个不同谱区,在四种分类标准条件下进行土壤质地分类分析方法研究。结果表明：(1)土壤化学组成的信息主要体现在近红外光谱的谱峰特征,而质地等物理信息主要反映在光谱的斜率、截距参数上,且二者在不同谱区的相对强度不同;(2)近红外光谱方法对土壤质地的分辨能力较低,随着分类粗化而有所提高;(3)在4组分类标准中土壤质地最高预测准确度为72％,其中在砂粒<70％和粘粒<40％条件下,预测准确度达到85％;(4)样本顶部漫反射光谱方法与扩展谱区范围均可有效提高质地预测准确度,而高精度仪器并不具备明显优势。     

Proton induced reactions of151Eu and153Eu up to Ep = 52MeV

Excitation functions for the proton induced reactions on¹⁵¹Eu and¹⁵³Eu have been measured by activation method up to E_p = 52MeV. The measurements are carried out on reactions to the residual nuclei—^{146,147,148,149,151,153}Gd and^{146,147,148,149}Eu. The measured excitation functions are discussed with the theory based on the statistical model of the compound nucleus.     

Effect of environment on fracture of ceramics

This paper reviews the important work to date describing the effect of environment (particularly H₂O) on the fracture behavior of glasses, single crystals and polycrystalline ceramics. It is shown that since the environment predominantly affects rates of crack propagation, fracture mechanics techniques have proved useful in describing the phenomenon of ⪡ stress corrosion ⪢ in ceramics. Models describing the environment- crack interaction are presented and mechanisms of crack propagation are discussed. The temperature dependence of ⪡ stress corrosion ⪢ in ceramics is described and the effect of plastic deforcation on a material's environmental sensitivity is briefly discussed. Finally, future research topics are suggested.     

The influence of starting material characteristics on the properties of high-porosity forsterite bricks

In order to follow the interdependence between characteristics of raw materials and properties of low bulk density bricks several sample series on forsterite basis were made. The starting powders we employed in the brick production were dead-burned magnesite and dunite having different physico-chemical properties: impurity content, granulation, crystal structure and other relevant parameters. Using the cold and vibro pressing and sintering techniques bricks of total porosity 44% and 70% were produced. The bricks contained predominantly macropores having various shape: spherical, irregural and elongated. The relationship obtained between powder granulation, mineral and chemical composition and thermal conductivity, gas permeability, thermostability, mechanical and other properties were discussed.     

基于内置电光晶体F P标准具的扫描滤波方法

基于内置电光晶体的F-P标准具,利用F-P多光束干涉原理和晶体的线性电光效应,提出了一种能有效提高啁啾脉冲信噪比的扫描滤波方法。给出了电光晶体加载电压的时变函数表达式,分析了影响信噪比提升效果的主要因素,并重点讨论了电光晶体的电压控制参数对信噪比提升效果和滤波器透过率的影响。研究结果表明,利用该扫描滤波方法可将啁啾脉冲激光信噪比提升约2个量级。