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Journal of Systems Science & Complexity 2014年第4期27卷 729-742页

作者： zhou pu LU Fengbin WANG Shouyang Risk Management Unit Bank of China Head Office Academy of Mathematics and Systems Science Chinese Academy of Sciences

supported by the National Natural Science Foundation of China under Grant Nos.71125005 70871108 and 70810107020;; Outstanding Talents Funds of Organization Department Beijing Committee of CPC

关键词： China stock market negative volatility spillover nonlinear Granger causality test riskabsorption volatility spillover.

Modelling and numerical simulation of isothermal oxidation of an individual magnetite pellet based on computational fluid dynamics

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Journal of Iron and Steel Research International 2021年第7期28卷 799-808页

作者： zhou pu Feng zhou Yue Sun Ming Zhang Bo-quan Li Department of Instrumentation Science and Technology Jiangsu UniversityZhenjiang 212013JiangsuChina

A mathematical model based on the computational fluid dynamics method,heat and mass transfer in porous media and the unreacted shrinking core model for the oxidation reaction of an individual magnetite pellet during preheating was *** commercial software COMSOL Multiphysics was used to simulate the change in the oxidation degree of the pellet at different temperatures and oxygen concentrations,and the simulated results were compared with the exper-imental *** model considered the influence of the exothermic heat of the reaction,and the enthalpy change was added to calculate the heat released by the *** results show that the oxidation rate on the surface of the pellet is much faster than that of the inside of the *** and oxygen concentration have great influence on the pellet oxidation ***,the exothermic calculation results show that there is a non-isothermal phenomenon inside the pellet,which leads to an increase in temperature inside the single *** the preheating condition of 873-1273 K(20%oxygen content),the heat released by the pellet oxidation reaction in a chain grate is 7.8×10^(6)-10.8×10^(6) kJ/h,which is very large and needs to be considered in the magnetite pellet oxidation modelling.

关键词： Magnetite pellet Oxidation Numerical simulation Unreacted shrinking core model Computational fluid dynamics

FOURTH ORDER EVOLUTION EQUATIONS WITH SLOWLY VARYING DEPTH AND CURRENT AND STABILITY OF STOKES WAVES

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Journal of Hydrodynamics 1991年第4期3卷 21-42页

作者： Chin-pu, zhou Yan-sheng, Chen Zhongshan Univ Guangzhou China

Fourth order evolution equations with slowly varying depth and current have been derived for two-dimensional modulation Stokes waves in arbitrary water depth. In the absence of current and variation of topography the equations reduce to those of Brinch-Nielsen & Jonsson, and the third order terms agree with those of Turpin & Benmoussa & Mei. Stokes wave in the slowly varying depth and current is specified, and its instability to small sidebands is studied in detail. A general criterion of instability with growth rate 0(Ε2) is given, and the maximum growth rate has also been obtained. An interesting result is that in the fourth-order theory the existence of current and varying depth leads the Stokes wave to be always unstable to small sidebands disturbance.

关键词： Mathematical Techniques Applications Mathematical Techniques Perturbation Techniques Water Waves Mathematical Models

Numerical modeling of the thermally induced core laser leakage in high power co-pumped ytterbium doped fiber amplifier

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High Power Laser Science and Engineering 2018年第2期6卷 83-91页

作者： Lingchao Kong Jinyong Leng pu zhou Zongfu Jiang College of Optoelectronic Science and Engineering National University of Defense TechnologyChangsha 410073China Hunan Provincial Key Laboratory of High Energy Laser Technology Changsha 410073China Hunan Provincial Collaborative Innovation Center of High Power Fiber Laser Changsha 410073China

We propose a novel model to explain the physical process of the thermally induced core laser leakage(TICLL) effect in a high power co-pumped ytterbium doped fiber(YDF) amplifier. This model considers the thermally induced mode bending loss decrease and the thermally induced mode instability(TMI) in the coiled YDF, and is further used to reproduce the TICLL effect in the high power co-pumped step-index 20/400 fiber amplifier. Besides, the TICLL effect in the copumping scheme and counter-pumping scheme is compared. The result proves that the TICLL effect is caused by the combined effect of the thermally induced mode bending loss decrease and the TMI, and could be mitigated by adopting the counter-pumping scheme. To our best knowledge, this is the first theoretical explanation of the TICLL effect in high power fiber amplifier.

关键词： design laser amplifiers laser systems modeling optimization

A high-power narrow-linewidth 1018 nm fiber laser based on a single-mode–few-mode–single-mode structure

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High Power Laser Science and Engineering 2015年第3期3卷 71-74页

作者： Man Jiang pu zhou Hu Xiao Pengfei Ma College of Optoelectronic Science and Engineering National University of Defense Technology

We demonstrate an all-fiber high-power Yb-doped 1018 nm fiber laser with a Gaussian-shaped output beam profile based on a mismatched structure, which consists of a pair of single-mode fiber Bragg gratings and a section of few-mode double-cladding gain fiber. The output power is up to 107.5 W with an optical-to-optical efficiency of 63%, and the 3 d B band is 0.26 nm at this power level. Such a structure of single-mode–few-mode–single-mode fiber oscillator can be used to generate high-power narrow-linewidth lasing with excellent beam quality in other spectral ranges.

关键词： fiber laser 1018 nm laser

Towards tapered-fiber-based all-fiberized high power narrow linewidth fiber laser

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Science China(Technological Sciences) 2018年第7期61卷 971-981页

作者： HUANG Long zhou ZiChao SHI Chen TAO RuMao MA PengFei WANG XiaoLin zhou pu College of Optoelectronic Science and Engineering National University of Defense TechnologyChangsha 410073China Hunan Provincial Collaborative Innovation Center of High Power Fiber Laser Changsha 410073China

Yb-doped fiber laser(YDFL) is a promising kind of laser source due to high efficiency, excellent beam quality, robust configuration, diverse applications and so on. The progress of large-mode-area double cladding active fiber and high power laser diodes have been continuously promoting the power scaling of the YDFLs. However, the further power scaling is blocked by some physic issues including nonlinear effect, thermal-induced mode instability(MI), optical damage and so forth. So, newlydesigned fibers with special structures are invented to address or relieve these limitations. The tapered fiber, which has changed mode area along its longitudinal direction, has been demonstrated to benefit suppressing the nonlinear effect, especially the stimulated Brillouin scattering(SBS) effect. In this paper, we will review the previous work done to explore the advantages of the tapered fiber for high power output, and then for the first time to our knowledge, demonstrate an all-fiberized high power narrow linewidth fiber laser based on a homemade tapered Yb-doped fiber(T-YDF). As a result, an output power of 260 W with a narrow linewidth of ~2 GHz is obtained, with SBS effectively suppressed owing to gradually increased mode area of the T-YDF as well as continuously changed Brillouin frequency shift dependent on the core diameter. Further power scaling is limited by MI, and the features of MI are studied in detail. It is pointed out that, the MI seems the primary and durative limitation factor of the tapered fiber amplifier for high power narrow linewidth output due to the gradually increased effective numerical aperture(NA) and the excitation of the high-order modes, even although it has the advantage to reduce other nonlinear effects. At last,worthwhile discussion about the optimization of the T-YDF and the whole fiber laser system for both SBS and MI suppression is conducted based on the previous and our results. It is concluded that the small diameter at the small-diameter

关键词： tapered Yb-doped fiber high power narrow linewidth stimulated Brillouin scattering mode instability

Development status of high power fiber lasers and their coherent beam combination

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Science China(Information Sciences) 2019年第4期62卷 56-87页

作者： Zejin LIU Xiaoxi JIN Rongtao SU Pengfei MA pu zhou College of Advanced Interdisciplinary Studies National University of Defense Technology

High-power fiber laser has been emerged great potential in a wide range of applications and becomes a robust candidate for high energy solid state laser system. To further increase the output brightness of single-channel fiber laser, high-brightness pump sources and high-power-handling passive components should be fabricated and utilized in the fiber laser systems, in addition to the advanced techniques for multiple nonlinear effects managements. The state-of-the-art high power fiber lasers are reviewed, in terms of narrow-linewidth fiber lasers, broadband fiber lasers and fiber lasers at 2 μm. Coherent beam combining is a promising technique to obtain higher output power while maintaining excellent beam quality simultaneously,which breaks through the bottlenecks of single-channel fiber laser. Based on a series of key techniques for coherent beam combining, high-power coherent beam combining of fiber lasers could be enabled with high combining efficiency. In this paper, we review the progress of high-power fiber lasers and their coherent beam combining in the recent decade, particularly the relevant work in our group. The future prospects of fiber lasers and coherent beam combining technique are also discussed.

关键词： fiber lasers and amplifiers nonlinear effects and mode instability coherent beam combining passive components 2 μm fiber lasers

kW-class high power fiber laser enabled by active long tapered fiber

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High Power Laser Science and Engineering 2018年第2期6卷 27-31页

作者： Chen Shi Hanwei Zhang Xiaolin Wang pu zhou Xiaojun Xu College of Advanced Interdisciplinary Studies National University of Defense TechnologyChangsha 410073China Hunan Provincial Collaborative Innovation Center of High Power Fiber Laser Changsha 410073China

Compared with traditional uniform fibers, tapered fiber has numerous unique advantages, such as larger mode area,higher pump absorption, suppression to nonlinear effects, and maintaining good beam quality. In this manuscript, we have constructed an all-fiberized fiber amplifier which is based on a piece of ytterbium-doped tapered double-clad fiber(T-DCF). The fiber amplifier is operated under continuous wave(CW) regime at 1080 nm wavelength. The M2 factor of the amplifier at 1.39 k W output power is ～1.8. The maximum output power of the system reached 1.47 k W, which, to the best of our knowledge, is the highest output power of long tapered fiber based fiber laser system. Our result successfully verifies the potential of power scalability and all-fiberized capability of long tapered fiber, and the performance of our system can be further enhanced by fiber design optimization.

关键词： fiber lasers and applications laser amplifiers

Power scaling on tellurite glass Raman fibre lasers for mid-infrared applications

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High Power Laser Science and Engineering 2018年第2期6卷 74-82页

作者： Tianfu Yao Liangjin Huang pu zhou Bing Lei Jinyong Leng Jinbao Chen College of Opto-Electronic Science and Engineering National University of Defense Technology Academy of Ocean Science and Engineering National University of Defense Technology

The power scaling on mid-infrared Raman fibre lasers(RFLs) is in demand for applications in health, environment and security. In this paper, we present the simulated laser behaviours of the tellurite glass RFLs pumped by 300-W Tm-doped fibre lasers(TDFLs) at 2 μm for the first time. By combining the advantages of the TDFLs and tellurite fibre, the output power at 2.35 μm has reached over hundreds of watts by first-order Raman shift. Moreover, the cascaded RFLs have been demonstrated with a wavelength extension greater than 3 μm and output power of tens of watts. To maximize the output power and the slope efficiency of the RFLs, we further analyse the interaction between the Raman gain and cavity loss, which are determined by fibre length and output reflectance of the laser cavity.

关键词： mid-infrared fibre lasers Raman fibre lasers stimulated Raman scattering tellurite glass fibre

Research on Multi-robot Coordination Searching Ignition Sources Approach

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Journal of Harbin Institute of Technology(New Series) 2013年第2期20卷 50-54页

作者： Jun Li Wen-Long Song pu-Cheng zhou College Mechanical and Electrical Northeast Forestry University Dept. of Information Engineering Artillery Academy of PLA

For the purpose of study on forecasting forest fire behavior,a probability approach was presented to search ignition sources by multi-robot coordination. Firstly,the environment map is built based on Bayes rules. Then,the probability searching strategy based on the environment map was designed. Every grid of the searching area was assigned searching expectation value, and robots selected the grid with the highest expectation value as its searching target. The simulation results show the search time reduces greatly,which proves the feasibility and validity of the given algorithm under unknown fire condition.

关键词： fire-fighting robots Bayes rules multi-robot coordination