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Investigation on nonlinear lateral-torsional coupled vibration of a rotor system with substantial unbalance

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Chinese Journal of Aeronautics 2020年第6期33卷 1642-1660页

作者： jie HONG Pingchao YU Yanhong ma Dayi ZHANG School of Energy and Power Engineering Beihang UniversityBeijing 100083China Collaborative Innovation Center of Advanced Aero-Engine Beihang UniversityBeijing 100083China Beijing Key Laboratory of Aero-Engine Structure and Strength Beijing 100083China

Substantial unbalance may be caused by fan blade off during the operation period of gas turbine engines,and related dynamic problems are very critical to the safety design of rotor system in *** article aims to understand lateral-torsional coupled vibration of the rotor system with substantial *** governing equation of a modified unbalanced rotor system is established based on Lagrangian ***,a mathematical analytical method is proposed in which a linear approximation is derived and the Floquet theory and Hill’s method are incorporated,from which the modal characteristics of the unbalanced rotor are *** modal characteristics of the unbalanced rotor system are revealed comprehensively for the first ***,the relation between the modes and responses of the unbalanced rotor is discussed in *** results show that the lateral vibration and torsional vibration of the unbalanced rotor are coupled through the inertial terms in the governing *** to the coupling,veering and lock-in phenomena occur between the frequencies of the forward whirl mode and the torsional ***,lock-in can lead to a kind of principal *** regard to the response of the unbalanced rotor,both natural vibration components and enforced vibration components appear in the lateral response,while only natural vibration components appear during torsional ***,natural vibration components play a crucial role in the response within the principal instability region and cause divergence of the vibration amplitudes in the lateral and torsional directions.

关键词： Instability Lateral-torsional coupled vibration Lock-in phenomenon Modes Unbalanced rotor

OPTIMIZATION OF DISPLACEMENT AND GLIDING PATH AND IMPROVEMENT OF PERFORmaNCE FOR AN UNDERWATER THERmaL GLIDER

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Journal of Hydrodynamics 2010年第5期22卷 618-625页

作者： YANG Hai ma jie State Key Laboratory of Ocean Engineering Shanghai Jiao Tong University Shanghai 200030 China

The underwater thermal glider utilizes ocean thermal energy to change its buoyancy, which enables it to ascend and descend. A Phase Change material （PCM） as the working fluid inside the thermal engine tubes is sensitive to the surrounding seawater temperature, whose effects are different with the various displacements and gliding angles of the glider. In this paper, the effects of the displacement and the gliding angle on the performance of the thermal engine were studied numerically and experimentally. On this basis, the ways to eliminate the negative effect of a thermocline on the performance of the thermal engine were obtained. The results show that the displacement and gliding angle affect the transition time of the PCM. There exist the threshold values of the displacement and gliding angle for the normal work of thermal engine. There are two means of eliminating the negative effect of a thermocline on the performance of the thermal engine and improving glider performance： one is to increase the displacement, and the other is to decrease the absolute value of the gliding angle. There is also another better way to improve glider performance.

关键词： displacement gliding angle underwater thermal glider Phase Change material (PCM)

Applications of structural efficiency assessment method on structural-mechanical characteristics integrated design in aero-engines

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Chinese Journal of Aeronautics 2020年第4期33卷 1260-1271页

作者： jie HONG Tianrang LI Huaqiang ZHENG Yanhong ma School of Energy and Power Engineering Beihang UniversityBeijing 100083China Collaborative Innovation Center of Advanced Aero-Engine Beijing 100083China AECC Hunan Aviation Powerplant Research Institute Zhuzhou 412002China

In the design process of advanced aero-engines,it is necessary to carry out an effective analysis method between structural features and mechanical characteristics for a better structural *** on the structural composition and functions of aero-engines,the concept and contents of structural efficiency can reflect the relation between structural features and mechanical *** order to achieve the integrated design of structural and mechanical characteristics,one quantitative analysis method called Structural Efficiency Assessment Method(SEAM)was put *** structural efficiency coefficient was obtained by synthesizing the parameters to quantitatively evaluate the aero-engine structure design *** method to evaluate structural design quality was *** analyzing the structural features of an actual dual-rotor system in typical high bypass ratio turbofan engines,the mechanical characteristics and structural efficiency coefficient were *** efficiency coefficient of high-pressure rotor(0.43)is higher than that of low-pressure rotor(0.29),which directly shows the performance of the former is better,there is room for improvement in structural design of the low-pressure *** the direction of structural optimization was pointed *** applications of SEAM shows that the method is operational and effective in the evaluation and improvement of structural design.

关键词： Aero-engines Integrated design Mechanical characteristics Structural efficiency Structural optimization

Dual Control Methods for a Mixed Control Problem with Optimal Stopping Arising in Optimal Consumption and Investment

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Numerical mathematics(Theory,Methods and Applications) 2022年第3期15卷 641-661页

作者： Jingtang ma jie Xing Shan Yang School of mathematics Southwestern University of Finance and EconomicsChengdu 611130China Guiyang Institute for Big Data and Finance Guizhou University of Finance and EconomicsGuiyang 550025China

This paper studies a problem of optimal investment and consumption with early retirement option under constant elasticity variation(CEV)model with finite *** risky assets are involved in the model with one following geometric Brownian motion and the other a CEV *** problem is a kind of two dimensional mixed control and optimal stopping problems with finite *** existence and continuity of the optimal retirement threshold surfaces are proved and the working and retirement regions are characterized ***-squares Monte-Carlo methods are developed to solve this mixed control and optimal stopping *** algorithms are well implemented and the optimal retirement threshold surfaces,optimal investment strategies and the optimal consumptions are drawn via examples.

关键词： Optimal investment and consumption stochastic control with optimal stopping nonlinear free boundary problems least-squares Monte-Carlo methods

Adsorption of toluene, ethylbenzene and xylene isomers on multi-walled carbon nanotubes oxidized by different concentration of NaOCI

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Frontiers of Environmental Science & Engineering 2012年第3期6卷 320-329页

作者： Fei YU jie ma Yanqing WU School of Environmental Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China State Key Laboratory of Pollution Control and Resource Reuse School of Environmental Science and EngineeringTongji UniversityShanghai 200092China

Multi-walled carbon nanotubes （MWCNTs） were fabricated and oxidized by different concentrations of sodium hypochlorite （NaOC1） solutions. The untreated MWCNTs and modified MWCNTs were employed as adsorbents to study their characterizations and adsorption performance of toluene, ethylbenzene and xylene isomers （TEX） in an aqueous solution. The physicochemical properties of MWCNTs were greatly affected after oxidation, which influences TEX adsorption capacity. The 3% NaOCl-oxidized MWCNTs shows the greatest enhancement in TEX adsorption, followed by the 30% NaOCl. More interestingly, the 15% NaOCl-oxidized MWCNTs has lower adsorption capacities than untreated MWCNTs. The adsorption mechanism of TEX on treated MWCNTs is attributed to the combined action of hydrophobic interaction, π-π bonding interaction between the aromatic ring of TEX and the oxygen-containing functional groups of MWCNTs and electrostatic interac- tion. 3% NaOCl solution could not only introduce much oxygen-containing functional groups on MWCNTs, but also lead to less damage for the pore structure. This suggests that the CNTs-3% NaOCl is efficient adsorbent for TEX and that they may possess good potential for TEX removal in wastewater treatment.

关键词： adsorption toluene ethylbenzene and xylene isomers (TEX) multi-walled carbon nanotube surface oxidation

Improved Ligand-Field Calculation of Energy Spectrum and R-Line Thermal Shift of MgO：Cr^3＋

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Communications in Theoretical Physics 2007年第5期47卷 937-943页

作者： ZHANG Zheng-jie ma Dong-Ping College of Information Engineering Chengdu University of Technology Chengdu 610059 China Department of Applied Physics Sichuan University Chengdu 610065 China

Traditional ligand-field theory has to be improved by taking into account both pure electronic contribution and electron-phonon interaction one （including lattice-vibrational relaxation energy）. By means of improved ligand-field theory, the R-line, t^3 2^2 T1 lines, t^2 2（^3 T1）e^4 T2, and t^2 2（^3T1）e^4T1 bands, ground-state g factor, four strain-induced level- splittings, and R-line thermal shift of MgO：Cr^3＋ have been calculated. The results are in very good agreement with the experimental data. It is found that for MgO：Cr^3＋, the contributions due to electron-phonon interaction （EPI） come from the first-order term. In thermal shift of R-line of MgO：Cr^3＋, the temperature-dependent contribution due to EPI is dominant.

关键词： improved ligand-field theory electron-phonon interaction energy spectrum strain-induced splitting thermal shift g factor

Pressure-Induced Shifts of R1 and R2 Lines of YAG：Cr3＋

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Communications in Theoretical Physics 2006年第4期45卷 754-760页

作者： ZHANG Zheng-jie ma Dong-Ping College of Information Engineering Chengdu University of Technology Chengdu 610059 China Department of Applied Physics Sichuan University Chengdu 610065 China

By means of improved ligand-field theory, the ＂pure electronic＂ pressure-induced shifts （PS＇s） and the PS＇s due to electron-phonon interaction （EPI） of R1 line and R2 line of YAG：Cr^3＋ have been calculated, respectively. The calculated results are in very good agreement with the experimental data. It is demonstrated that the admixture of │t^2 2（^3T1）e^4T2〉 and │t^3 2 ^2E〉 bases in the wavefunction of RI level of YAG：Crs＋ and its change with pressure play a key role for the PS of RI line. The behaviors of the ＂pure electronic＂ PS of RI line and the PS of RI line due to EPI are different. It is the combined eEect of them that gives rise to the total PS of R1 line, which has satisfactorily explained the experimental results. The systematic analyses and comparisons between the feature of R1-line PS of YAG：Cr^3＋ and the ones of three laser crystals （GSGG：Cr^3＋, GGG：Cr^3＋ and ruby） have been made, and the origin of the difference between them has been revealed.

关键词： high-pressure effect electron-phonon interaction R lines admixture of |t22(3T1)e4T2〉 and |t322E〉 laser crystals

Improved Ligand-Field Theoretical Calculation of R-Line Pressure-Induced Shift of MgO:V^(2+)

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Communications in Theoretical Physics 2008年第9期50卷 781-786页

作者： ZHANG Zheng-jie ma Dong-Ping Department of Physics Chengdu University of Technology Chengdu 610059 China Department of Applied Physics Sichuan University Chengdu 610065 China

By means of an improved ligand-field theory, the ＂pure electronic＂ PS and the PS due to EPI of R line of MgO： V^2＋ have been calculated, respectively. The calculated results are in very good agreement with the experimental data. The behaviors of the pure electronic PS of R line of MgO：V^2＋ and the PS of its R line due to EPI are different. It is the combined effect of them that gives rise to the total PS of R line, which has satisfactorily explained the experimental results. The mixing-degree of ｜t2^2（^3T1）e^4T2〉 and ｜t2^3 ^2E〉 in the wavefunetion of R level and its variation with pressure have been calculated and analyzed. The comparison between the feature of R-line PS of MgO：V^2＋ and that of MgO：Cr^3＋ has been made.

关键词： high-pressure effect electron-phonon interaction R line improved ligand-field theory the admix-ture of |t2^2(^3T1)e^4T2〉 and |t2^3 2E〉

Simulated Sensitivity of the Tropical Cyclone Eyewall Replacement Cycle to the Ambient Temperature Profile

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Advances in Atmospheric Sciences 2017年第9期34卷 1047-1056页

作者： Xulin ma jie HE Xuyang GE Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Key Laboratory of Meteorological DisasterNanjing University of Information Science and Technology

In this study, the impacts of the environmental temperature profile on the tropical cyclone eyewall replacement cycle are examined using idealized numerical simulations. It is found that the environmental thermal condition can greatly affect the formation and structure of a secondary eyewall and the intensity change during the eyewall replacement cycle. Simulation with a warmer thermal profile produces a larger moat and a prolonged eyewall replacement cycle. It is revealed that the enhanced static stability greatly suppresses convection, and thus causes slow secondary eyewall formation. The possible processes influencing the decay of inner eyewall convection are investigated. It is revealed that the demise of the inner eyewall is related to a choking effect associated with outer eyewall convection, the radial distribution of moist entropy fluxes within the moat region, the enhanced static stability in the inner-core region, and the interaction between the inner and outer eyewalls due to the barotropic instability. This study motivates further research into how environmental conditions influence tropical cyclone dynamics and thermodynamics.

关键词： tropical cyclone eyewall replacement cycle ambient temperature profile