内腔四程放大高功率激光系统寄生振荡

 基于小信号增益公式、菲涅耳反射公式和判断内腔四程放大高功率激光系统寄生腔增益与损耗大小,研究了2个光路构型相似,寄生腔构成相近的高功率固体激光装置（装置A和装置B）的系统寄生振荡问题:首先指出了系统中存在可能起振的3个寄生腔,然后分析了3个寄生腔中影响损耗的各个因素,根据装置A上的实验结果,判断在仅通过钕玻璃片检偏的情况下,装置B的第3寄生腔存在产生寄生振荡的可能性,最后采取加入一组偏振片的方法抑制寄生振荡。     

Carrier dynamics and dispersive terahertz Bloch gain in semiconductor superlattices

We have directly determined the spectral shape of the complex conductivities of Bloch oscillating electrons by using time-domain terahertz (THz)-electrooptic sampling technique and presented an experimental evidence for a dispersive Bloch gain in superlattices. This unique dispersive gain without population inversion arises from a non-classical nature of Bloch oscillations; i.e., the phase of the Bloch oscillation is shifted by π/2 from that of the semi-classical charged harmonic oscillation when driven by the same AC field. By increasing the bias electric field, the gain bandwidth reached in our particular sample.     

Oscillation for a nonlinear dynamic system on time scales

We study the oscillation properties of a system of two first-order nonlinear equations on time scales. This form includes the classical Emden–Fowler differential and difference equations and many of its extensions. We generalize some well-known results of Atkinson, Belohorec, Waltman, Hooker, Patula and others and also describe the relation to solutions of a delay-dynamic system.     

Oscillation criteria for third-order nonlinear differential equations

In this paper, we are concerned with the oscillation properties of the third order differential equation

本刊英文版Vol.38(2022),No.2论文摘要北大核心CSCD

Global Fujita-Kato’s Type Solutions and Long-time Behavior for the Multidimensional Chemotaxis Model Qiong Lei CHEN Xiao Nan HAO Jing Yue LI Abstract We establish the global well-posedness for the multidimensional chemotaxis model with some classes of large initial data,especially the case when the rate of variation of ln v_(0)(v_(0) is the chemical concentration)contains high oscillation and the initial density near the equilibrium is allowed to have large oscillation in 3D.     

Study on electrochemical fingerprints of different Chrysanthemums by using B-Z oscillation system

A sensitive and convenient method for the study of electrochemical fingerprints of Chrysanthemums from different regions is studied by Belousov-Zhabotinskii(B-Z) oscillation system with malonate as a dissipative material.The results indicated that the electrochemical fingerprints of Chrysanthemums from different regions show significantly different characteristics,and can be used to identify the regions of Chrysanthemums.     

A remedy for numerical oscillations in weakly compressible smoothed particle hydrodynamics

Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) can lead to non‐physical oscillations in the pressure and density fields when simulating incompressible flow problems. This in turn may result in tensile instability and sometimes divergence. In this paper, it is shown that this difficulty originates from the specific form of spatial discretization used for the pressure term when solving the mass conservation equation. After describing the pressure–velocity decoupling problem associated with the so‐called colocated grid methods, a modified approach is presented that overcomes this problem using a different discretization scheme for the second derivative of pressure. The modified scheme is employed for solving a number of benchmark problems including both single‐phase and two‐phase test cases. Copyright © 2010 John Wiley & Sons, Ltd.     

非正弦周期性外力作用下受迫振动的图像：磁力摆应用之四

本文主要介绍和讨论用磁力摆进行行的，在非正弦周期性外力作用下受迫振动的实验结果，并十分清楚地显示了受迫振动的较为完整的图像。     

间歇釜中BZ类均相无机振荡反应的研究

在间歇釜中, 以BrO3^--H2PO2^--Mn^2^+-Fe(phen)3^2^+-H2SO4为体系, 本文首次设计了一个纯无机均相BZ类化学振荡体系, 采用溴离子选择性电极和紫外可见分光光度计可分别观察到[Br^-],[Mn^3^+]和[Fe(phen)3^3^+]的振荡现象。对振荡反应产物及总反应计量关系进行了分析, 考察了反应物浓度和反应温度对体系振荡反应的影响, 并由此计算得到振荡反应的表观活化能, 研究了Cl^-,Br^-, Br2, 丙烯腈等因素对振荡反应的影响, 并由此对振荡反应的控制机理作了探索。对体系中两种金属离子的作用进行了分析。在此基础上提出了一种在间歇釜中设计均相BZ类振荡反应的新方法。利用这一方法, 不仅可以设计无机振荡反应, 而且还可以设计一系列由氨基酸、多肽、糖类等具有生物功能的物质参与的化学振荡, 有助于理解生物体内普遍存在的周期性现象。     

The Earth effects on the supernova neutrino spectra

The Earth effects on the energy spectra of supernova neutrinos are studied. We analyze numerically the time-integrated energy spectra of neutrino in a mantle–core–mantle step function model of the Earth's matter density profile. We consider a realistic frame-work in which there are three active neutrinos whose mass squared differences and mixings are constrained by the present understanding of solar and atmospheric neutrinos. We find that the energy spectra change for some allowed mixing parameters. Especially, the expected number of events at SNO shows characteristic behavior with respect to energy, i.e., a great dip and peak. We show that observations of the Earth effect allow us to identify the solar neutrino solution and to probe the mixing angle θ₂.