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Transition prediction of the supersonic boundary layer on a cone under the consideration of receptivity to slow acoustic waves

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Science China(Physics,Mechanics & Astronomy) 2011年第10期54卷 1875-1882页

作者： SU CaiHong zhou heng Department of Mechanics Tianjin University Tianjin 300072 China Tianjin Key Laboratory of Modern Engineer Mechanics Tianjin 300072 China

Transition prediction of the supersonic boundary layer on a cone with small angle of attack and Mach number 3.5 is investi-gated under the consideration of receptivity to slow acoustic waves, as the acoustic waves are the main environmental distur-bances in a conventional, i.e. non-quiet, wind tunnel. It is shown that the e-N method can still yield fairly satisfactory results incomparison with those obtained in wind tunnel experiments, provided that the boundary layer receptivity to slow acousticwaves is properly taken into account, including the dependence of the amplitude of disturbances on the frequency andstream-wise location. Neither the conventional e-N method nor the improved e-N method can yield correct result of transitionprediction, because the receptivity mechanisms considered there are not in accord with the real situation in the wind tunnel.

关键词： receptivity boundary layer transition cone e-N method

A simulation on bypass transition and its key mechanism

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Science China(Physics,Mechanics & Astronomy) 2013年第4期56卷 775-784页

作者： DONG Ming zhou heng Department of Mechanics Tianjin University Tianjin Key Laboratory of Modern Engineering Mechanics

The scenario of bypass transition is generally described theoretically as follows: low-frequency disturbances in the free-stream would generate long stream-wise streaks in the boundary layer, which later would induce secondary instability, leading to rapid increase of high-frequency disturbances, then possibly turbulent spots would emerge, and through their merging, fully developed turbulence appears. This description, however, is insufficient in the sense that it does not provide the explanation on why during the breakdown stage, a large number of waves with different frequencies and wave numbers would appear almost simultaneously, leading to a swift change of the mean flow profile. In this paper, the mechanism leading to this phenomenon is found to be the change of the stability characteristics of mean flow profile, which has a positive feedback effect on the change of the profile itself. And another interesting finding is that, during the transition, the unstable disturbance waves which appear first belong to a branch of inviscid modes, while following the change of the stability characteristics of the mean flow profile, the disturbance waves will change to another branch of inviscid modes, and the latter play the key role in bypass transition.

关键词： bypass transition breakdown instability streak inviscid

Microstructure and Strength of Brazed Joints of Ti_(3)Al Base Alloy with Cu-P Filler Metal

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Journal of Materials Science & Technology 2005年第4期21卷 493-498页

作者： Peng HE Jicai FENG heng zhou National Key Laboratory of Advanced Welding Production Technology Harbin Institute of Technology Harbin 15{}001 China

Brazing of Ti3Al alloys with the filler metal Cu-P was carried out at 1173-1273 K for 60-1800 s. When products are brazed, the optimum brazing parameters are as follows： brazing temperature is 1215-1225 K; brazing time is 250-300 s. Four kinds of reaction products were observed during the brazing of Ti3Al alloys with the filler metal Cu-P, i.e., Ti3Al phase with a small quantity of Cu （Ti3Al（Cu）） formed close to the Ti3Al alloy; the TiCu intermetallic compounds layer and the Cu3P intermetallic compounds layer formed between Ti3Al（Cu） and the filler metal, and a Cu-base solid solution formed with the dispersed Cu3P in the middle of the joint. The interracial structure of brazed Ti3Al alloys joints with the filler metal Cu-P is Ti3Al/Ti3Al（Cu）/TiCu/Cu3P/Cu solid solution （Cu3P）/Cu3P/TiCu/Ti3Al（Cu）/Ti3Al, and this structure will not change with brazing time once it forms. The thickness of TiCu＋Cu3P intermetallic compounds increases with brazing time according to a parabolic law. The activation energy Q and the growth velocity/to of reaction layer TiCu＋Cu3P in the brazed joints of Ti3Al alloys with the filler metal Cu-P are 286 kJ/mol and 0.0821 m2/s, respectively, and growth formula was y2=O.O821exp（-34421.59/T）*** control of the growth for the reaction layer TiCu＋Cu3P can influence the final joint strength. The formation of the intermetallic compounds TiCu＋Cu3P results in embrittlement of the joint and poor joint properties. The Cu-P filler metal is not fit for obtaining a high-quality joint of Ti3Al brazed.

关键词： Brazed joints Microstructure Ti3Al base alloy

Intelligent Ironmaking Optimization Service on a Cloud Computing Platform by Digital Twin

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Engineering 2021年第9期7卷 1274-1281页

作者： heng zhou Chunjie Yang Youxian Sun The State Key Laboratory of Industrial Control Technology&College of Control Science and Engineering Zhejiang UniversityHangzhou 310027China

The shortage of computation methods and storage devices has largely limited the development of multiobjective optimization in industrial *** improve the operational levels of the process industries,we propose a multi-objective optimization framework based on cloud services and a cloud distribution ***-time data from manufacturing procedures are first temporarily stored in a local database,and then transferred to the relational database in the ***,a distribution system with elastic compute power is set up for the optimization ***,a multi-objective optimization model based on deep learning and an evolutionary algorithm is proposed to optimize several conflicting goals of the blast furnace ironmaking *** the application of this optimization service in a cloud factory,iron production was found to increase by 83.91 t∙d^(-1),the coke ratio decreased 13.50 kg∙t^(-1),and the silicon content decreased by an average of 0.047%.

关键词： Cloud factory Blast furnace Multi-objective optimization Distributed computation

Farm size and fertilizer sustainable use: An empirical study in Jiangsu, China

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Journal of Integrative Agriculture 2019年第12期18卷 2898-2909页

作者： HU Ling-xiao ZHANG Xiao-heng zhou Ying-heng China Institute for Rural Studies Tsinghua UniversityBeijing 100084P.R.China College of Economics and Management Huazhong Agricultural UniversityWuhan 430070P.R.China School of Economics Jiangxi University of Finance and EconomicsNanchang 330013P.R.China

Inefficient use of fertilizer has caused serious environmental problems and unsustainable development of agriculture in *** meet the increasing food demand in the future without damaging the ecological environment,Chinese government officially launched the Action Plan for the Zero Growth of Fertilizer Use in *** the same time,China released a series of policies aiming explicitly at expanding farm size and a great number of large scale farmers emerged ***,whether the expansion of farm size will be beneficial for the increase of fertilizer use efficiency still remains to be *** this study,we comprehensively explored the relationship between fertilizer use efficiency and farm *** on the 4281 farm households’survey data collected by the National Development and Reform Commission(NDRC)of China from 2004 to 2016 in Jiangsu Province,China,this paper applies a stochastic frontier production function to estimate fertilizer use efficiency across farm size and uses a regression model to analyze the influence of farm size on fertilizer use *** results show that:(1)the average fertilizer use efficiency of whole samples was only 0.60,much lower than the average technical efficiency,indicating that on average half of the fertilizer utilized are excessive in China;and(2)the smallest farm size group get the highest fertilizer use efficiency *** also provide some possible explanations for the inverse relationship between farm size and fertilizer use efficiency.

关键词： fertilizer use efficiency farm size China's rice production

Hyperspectral Image Classification Based on Capsule Network

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Chinese Journal of Electronics 2022年第1期31卷 146-154页

作者： MA Qiaoyu ZHANG Xin ZHANG Chunlei zhou heng School of Science China University of Geosciences (Beijing) School of Statistics Beijing Normal University Beijing Zhongdi Runde Petroleum Technology Co. Ltd.

The conventional convolutional neural network performs not well enough in the ground objects classification because of its insufficient ability in maintaining sensitive spectral information and characterizing the covariance of spatial structure, resulting from the narrow sensitive frequency band and complex spatial structure with diversity of hyperspectral remote sensing data which caused more serious phenomena of "same material, different spectra" and "different material, same spectra".Therefore, an improved capsule network is proposed and introduced into hyperspectral image target recognition. A convolution structure combining shallow features and multi-scale depth features is put forward to reduce the phenomena of "different material, same spectra" firstly,and then the diversity of the spatial structure is expressed by the capsule vector and sub-capsule division in channel wise, so that the averaging effect of the convolution process is weakened in the spectral domain and the spatial domain to reduce the phenomena of "same material, different spectra". By comparing the experimental results on the hyperspectral data sets such as Indian Pines,Salinas, Tea Tree and Xiongan, the capsule network shows strong spatial structure expression ability, flexible deep and shallow feature fusion ability in multi-scale, and its accuracy in target recognition is better than that of conventional convolutional neural networks, so it is suitable for the recognition of complex targets in hyperspectral images.

关键词： spectral domain spatial domain hyperspectral imaging different spectra insufficient ability complex targets geophysical image processing convolution process neural nets image classification object detection hyperspectral remote sensing data capsule vector shallow features hyperspectral image target recognition multiscale feature extraction geophysical signal processing flexible deep feature fusion ability shallow feature fusion ability convolution structure narrow sensitive frequency band strong spatial structure expression ability improved capsule network hyperspectral images serious phenomena complex spatial structure hyperspectral image classification sub-capsule division hyperspectral data sets remote sensing conventional convolutional neural network different material sensitive spectral information

The investigation of coherent structures in the wall region of a supersonic turbulent boundary layer based on DNS database

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Science China(Physics,Mechanics & Astronomy) 2007年第3期50卷 348-356页

作者： HUANG ZhangFeng zhou heng LUO JiSheng Department of Mechanics Tianjin UniversityTianjin 300072China Liu-Hui Center of Applied Mathematics Nankai University and Tianjin UniversityTianjin 300072China

Through temporal mode direct numerical simulation, flow field database of a fully developed turbulent boundary layer on a flat plate with Mach number 4.5 and Reynolds number Reθ =1094 has been obtained. Commonly used detection meth- ods in experiments are applied to detecting coherent structures in the flow field, and it is found that coherent structures do exist in the wall region of a supersonic turbulent boundary layer. The detected results show that a low-speed streak is de- tected by using the Mu-level method, the rising parts of this streak are detected by using the second quadrant method, and the crossing regions from a low-speed streak to the high-speed one are detected by using the VITA method respectively. Notwithstanding that different regions are detected by different methods, they are all accompanied by quasi-stream-wise vortex structures.

关键词： coherent structure turbulence conditional sampling method supersonic boundary layer direct numerical simulation

Design and fabrication of compact Ge-on-SOI coupling structure

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Frontiers of Optoelectronics 2019年第3期12卷 276-285页

作者： Jianfeng GAO Junqiang SUN heng zhou Jialin JIANG Yang zhou Wuhan National Laboratory for Optoelectronics School of Optical and Electronic InformationHuazhong University of Science and TechnologyWuhan 430074China

In this paper, we have proposed and demonstrated a simple approach to fabricate vertical integrated structure for coupling between active germanium (Ge) waveguide and silicon-on-insulator (SOI) waveguide. The active Ge waveguide is sputtered after etching the underlying passive silicon (Si) waveguide. This method scuttles away from the difficulty involved in the waveguide fabrication by avoiding the etching process for the Ge waveguide, and thereby the waveguide quality is improved. The influences of the coupling structural parameters on the coupling loss are analyzed and discussed. The optimizing parameters are obtained for the fabrication. The minimal coupling loss is experimentally measured about 2.37 dB, and variation tendency of coupling loss against the structural parameters is consistent with the theoretical result. The proposed approach offers an effective path for vertical coupling between Ge and SOI optical components.

关键词： taper coupler integrated optics device guided waves silicon-on-insulator (SOI) waveguide germanium (Ge) waveguide active Ge device Ge-on-SOI coupling structure

THE DELAY OF TRANSITION OF A LAMINAR BOUNDARY LAYER OVER COMPLIANT WALL

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Acta Mechanica Sinica 1990年第1期6卷 15-21页

作者： Li Wanping zhou heng Tianjin University Present address:Department of Mechanics Huazhong University of Science and TechnologyWuhan 430074

In a previous paper, a method has been developed to study the stability characteristics of laminar boundary layers over compliant walls. In this paper, the effect of double layered compliant wall and Kramer type compliant wall on delaying the transition is investigated, and it is shown that there does exist the possibility to de- lay the transition by applying such compliant walls.

关键词： transition compliant wall stability