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Lagrangian-based investigation of multiphase flows by finite-timeLyapunov exponents

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Acta Mechanica Sinica 2012年第3期28卷 612-624页

作者： Jia-ning tang Chien-Chou Tseng ning-FeiWang School of Aerospace Engineering Beijing Institute of Technology100081 Beijing China Department of Mechanical and Electro-Mechanical Engineering National Taiwan Sun Yat-Sen UniversityKaohsiung Taiwan China Department of Aerospace Engineering University of Michigan Ann ArborM148109 USA

Multiphase flows are ubiquitous in our daily life and engineering applications. It is important to investigate the flow structures to predict their dynamical behaviors ef- fectively. Lagrangian coherent structures （LCS） defined by the ridges of the finite-time Lyapunov exponent （FTLE） is utilized in this study to elucidate the multiphase interactions in gaseous jets injected into water and time-dependent turbu- lent cavitation under the framework of Navier-Stokes flow computations. For the gaseous jets injected into water, the highlighted phenomena of the jet transportation can be observed by the LCS method, including expansion, bulge, necking/breaking, and back-attack. Besides, the observation of the LCS reveals that the back-attack phenomenon arises from the fact that the injected gas has difficulties to move toward downstream re- gion after the necking/breaking. For the turbulent cavitating flow, the ridge of the FTLE field can form a LCS to capture the front and boundary of the re-entraint jet when the ad- verse pressure gradient is strong enough. It represents a bar- rier between particles trapped inside the circulation region and those moving downstream. The results indicate that the FFLE field has the potential to identify the structures of mul- tiphase flows, and the LCS can capture the interface/barrier or the vortex/circulation region.

关键词： Finite-time Lyapunov exponents Lagrangiancoherent structures Multiphase flow Gaseous jets injectedinto water Cavitation

Flow structures of gaseous jets injected into water for underwater propulsion

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Acta Mechanica Sinica 2011年第4期27卷 461-472页

作者： Jia-ning tang ning-Fei Wang Wei Shyy School of Aerospace Engineering Beijing Institute of Technology 100081 Beijing China Department of Aerospace Engineering University of Michigan Ann Arbor MI 48109 USA

Gaseous jets injected into water are typically found in underwater propulsion, and the flow is essentially unsteady and turbulent. Additionally, the high water-to-gas density ratio can result in complicated flow structures; hence measuring the flow structures numerically and experimentally remains a challenge. To investigate the performance of the underwater propulsion, this paper uses detailed NavierStokes flow computations to elucidate the gas-water interactions under the framework of the volume of fluid （VOF） model. Furthermore, these computations take the fluid compressibility, viscosity, and energy transfer into consideration. This paper compares the numerical results and experimental data, showing that phenomena including expansion, bulge, necking/breaking, and back-attack are highlighted in the jet process. The resulting analysis indicates that the pressure difference on the rear and front surfaces of the propul- sion system can generate an additional thrust. The strong and oscillatory thrust of the underwater propulsion system is caused by the intermittent pulses of the back pressure and the nozzle exit pressure. As a result, the total thrust in underwater propulsion is not only determined by the nozzle geometry but also by the flow structures and associated pressure distri- butions.

关键词： Gaseous jets - Underwater propulsion Highdensity ratio Gas-water interactions

ISAR target recognition based on non-negative sparse coding

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Journal of Systems Engineering and Electronics 2012年第6期23卷 849-857页

作者： ning tang Xunzhang Gao Xiang Li Institute of Space Electronic Technology National University of Defense Technology Changsha 410073 E R. China

Aiming at technical difficulties in feature extraction for the inverse synthetic aperture radar （ISAR） target recognition, this paper imports the concept of visual perception and presents a novel method, which is based on the combination of non-negative sparse coding （NNSC） and linear discrimination optimization, to recognize targets in ISAR images. This method implements NNSC on the matrix constituted by the intensities of pixels in ISAR images for training, to obtain non-negative sparse bases which characterize sparse distribution of strong scattering centers. Then this paper chooses sparse bases via optimization criteria and calculates the corresponding non-negative sparse codes of both training and test images as the feature vectors, which are input into k neighbors classifier to realize recognition finally. The feasibility and robustness of the proposed method are proved by comparing with the template matching, principle component analysis （PCA） and non-negative matrix factorization （NMF） via simulations.

关键词： inverse synthetic aperture radar (ISAR) pre-processing non-negative sparse coding (NNSC) visual percep-tion target recognition.

Deformation Calculation of Cross-section Based on Virtual Force in Thin-walled Tube Bending Process

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Chinese Journal of Mechanical Engineering 2009年第5期22卷 696-701页

作者： LIU Jingyao tang Chengtong ning Ruxin School of Mechanical Engineering Beijing lnstitute of Technology Beijing 100081 China

Cross-section deformation is one of important factors affecting the quality of tube formation, and the tube＇s capability of transporting liquid and gas will be reduced because of the cross-section ellipse deformation due to the effect of shear load in plastic bending process. When the tube is bent, the extrados-wall bears the tension stress and the intrados-wall bears the compression stress, synchronously the cross-section is affected by the circumferential stress. According to the above, the distribution function and curve of tangential stress can be obtained according to force balance differential equations on circumferential direction and Trasca rule. Subsequently the real state and virtual state moment equations were established, a new method was presented adopting the virtual principle of deformation system to calculate the x-axis and y-axis displacement of arbitrary point on cross-section. So the major and minor axes of deformed cross-section can be calculated according to the displacements of each point, and the variety value of major and minor axes will be obtained further. Finally the theoretical calculating result is compared with NC tube rotary-bending experiment results to verify the rationality of theoretical analysis, and the cross-section deformation rule of thin-walled tube can be received.

关键词： thin-walled tube stress analysis major and minor axes cross-section deformation virtual force

Preparation of Modified Composite Nanofiltration Membrane Synergistically Using Carboxylic Multi-walled Carbon Nanotube and β-cyclodextrin

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Journal of Wuhan University of Technology(Materials Science) 2025年第1期 232-239页

作者：刘鹏 MAO Junpeng FANG Yanfeng YU Yunwu CHEN Changxiu tang ning WAN Ye GU Yaxin LIU Yunxue WANG Lihua School of Materials Science and Engineering Shenyang Jianzhu University

A new modified blend ultrafiltration （UF） membrane with good hydrophilicity,high porosity and excellent anti-fouling performance was developed by using carboxylic multi-walled carbon nanotube （CMWCNT） as casting solution ***,a composite nanofiltration （NF） membrane with large water flux and good retention rate was fabricated by using the PVDF/CMWCNT blend UF membrane as the substrate,and polyvinyl alcohol （PVA）,β-cyclodextrin （β-CD） and polyethylenimine （PEI） as the coating *** results show that with the appropriate addition of CMWCNT in the casting solution,the surface roughness,porosity and recovery rate of the PVDF/CMWCNT blend UF membrane is obviously *** water flux of blend UF membrane is significantly improved when the CMWCNT content increases from 0 wt% to 0.2 wt%.The water flux of blend UF membrane with 0.2 wt% CMWCNT is 162.7 L/（m2·h）,which is 44.3% higher than that of the pure PVDF *** β-CD content is 0.8 wt%,the retention rate of Congo red by PVDF/CMWCNT/β-CD composite NF membrane reaches 98.7%,which is 28.3% higher than that of single PVA/PEI modified *** research will provide a new idea and simple method for developing novel high-performance composite NF membranes.

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A variational formula for controlled backward stochastic partial differential equations and some application

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Applied Mathematics(A Journal of Chinese Universities) 2014年第3期29卷 295-306页

作者： MENG Qing-xin tang Mao-ning Department of Mathematics Huzhou Teachers College School of Mathematical Sciences Fudan University

An optimal control problem for a controlled backward stochastic partial differential equation in the abstract evolution form with a Bolza type performance functional is considered. The control domain is not assumed to be convex, and all coefficients of the system are allowed to be random. A variational formula for the functional in a given control process direction is derived, by the Hamiltonian and associated adjoint system. As an application, a global stochastic maximum principle of Pontraygins type for the optimal controls is established.

关键词： Variational formula stochastic evolution equation backward stochastic evolution equation,stochastic maximum principle spike variation.

Rheological Properties of Conductive Asphalt Binders Containing Graphite and Carbon Fiber Before and After Ageing

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Journal of Wuhan University of Technology(Materials Science) 2013年第3期28卷 557-559页

作者：孙长军 tang ning PAN Pan 吴少鹏 State Key Laboratory of Silicate Materials for Architectures Wuhan University of Technology Caofeidian Development Investment Group Co. LTD

Modified asphalt binders were prepared by adding conductive materials, graphite and carbon fiber. The rotation thin film oven test （RTFOT） and pressure age vessel test （PAV） were conducted to simulate the binder aging in the field. Rheological properties of graphite and carbon fiber modified asphalt binder were investigated by the empirically rheological properties （penetration and softening point） and the dynamic shear rheometer （DSR） test. Results show that physical properties of asphalt binder change with conductive material mixed. DSR tests present that the values of complex modulus increase while phase angles decrease under a proper amount of graphite and carbon fiber. Rutting parameters point out that graphite can improve the rutting resistance of asphalts. Rheological parameters can be used to assess aging.

关键词： graphite carbon fiber rheological properties aging

Influences of bubble size distribution on propagation of acoustic waves in dilute polydisperse bubbly liquids

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Journal of Hydrodynamics 2019年第1期31卷 50-57页

作者： Yu-ning Zhang Zi-biao Jiang Jin Yuan Ting Chen Yu-ning Zhang1 ning-ning tang Xiao-ze Du Key Laboratory of Condition Monitoring and Control for Power Plant Equipment (Ministry of Education) School of EnergyPower and Mechanical EngineeringNorth China Electric Power UniversityBeijing 102206China School of Science Wuhan Institute of TechnologyWuhan 430205China College of Mechanical and Transportation Engineering China University of Petroleum - BeijingBeijing 102249China Beijing Key Laboratory of Process Fluid Filtration and Separation China University of Petroleum-BeijingBeijing 102249China

The present paper studies the influences of the bubble size distribution on the propagation of acoustic waves in dilute polydisperse bubbly liquids *** proposed approach is validated by using available experimental data in the *** is revealed that the bubble size distribution has impacts on both the wave speed and the wave ***,the minimum wave speed together with the corresponding frequency could be both significantly affected by the bubble size distribution (e.g.,the standard deviation).Furthermore,the maximum wave attenuation in the frequency response curve is also sensitive to the variations of the bubble size distribution.

关键词： Cavitation gas bubbles wave propagation wave speed wave attenuation

Quantified simulation research on harmonious factors in the leadership teams of aerospace enterprise group

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Journal of Systems Engineering and Electronics 2007年第4期18卷 751-757页

作者： Yin Xingliang Hu Yunquan Yang Fuping hao Hanping tang ning Harbin Institute of Technology Harbin 150001 P. R. China China Aerospace Science & Industry Corp. Beijing 100830 P. R. China Beijing Normal University Beijing 100875 P. R. China

A brief account of basic connotation and evaluation indexes system of harmonious leadership teams is given. On this basis, a simulation model is built by using the ARENA simulation software and the quantified simulation is carried out for the factors of harmonization of aerospace enterprise leadership teams. Moreover, by taking the characteristics of aerospace enterprise leadership teams into consideration, the comparison of harmonization quantified results of several typical leadership teams, especially on the comparative analysis of influencing degrees of moral characters and capabilities on the leadership teams overall harmonization is emphatically discussed. Finally, a conclusion is drawn.

关键词： harmonization aerospace leadership teams quantified simulation ARENA