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Recent progress of machine learning in flow modeling and active flow control

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Chinese Journal of Aeronautics 2022年第4期35卷 14-44页

作者： Yunfei Li Juntao Chang chen kong Wen Bao School of Energy Science and Engineering Harbin Institute of TechnologyHarbin 150001China

In terms of multiple temporal and spatial scales, massive data from experiments, flow field measurements, and high-fidelity numerical simulations have greatly promoted the rapid development of fluid mechanics. Machine Learning(ML) provides a wealth of analysis methods to extract potential information from a large amount of data for in-depth understanding of the underlying flow mechanism or for further applications. Furthermore, machine learning algorithms can enhance flow information and automatically perform tasks that involve active flow control and optimization. This article provides an overview of the past history, current development, and promising prospects of machine learning in the field of fluid mechanics. In addition, to facilitate understanding, this article outlines the basic principles of machine learning methods and their applications in engineering practice, turbulence models, flow field representation problems, and active flow control. In short, machine learning provides a powerful and more intelligent data processing architecture, and may greatly enrich the existing research methods and industrial applications of fluid mechanics.

关键词： Data-driven modeling Flow control Flow field kinematics Machine learning Neural networks-applications

A deep learning approach for velocity field prediction in a scramjet isolator from Schlieren images

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Chinese Journal of Aeronautics 2023年第11期36卷 58-70页

作者： chen kong Ziao WANG Yunfei LI Juntao CHANG School of Energy Science and Engineering Harbin Institute of TechnologyHarbin 150001China

Accurate measurements of physical parameters in a scramjet isolator are very important to promote the design and optimization of the isolator and even the *** a ground experiment,limited by the inherent characteristics of measurement technology and equipment,it is a big challenge to obtain the velocity field inside an *** this study,a deep learning approach was introduced to combine data obtained from ground experiments and numerical simulations,and a velocity field prediction model was developed for obtaining the velocity field inside an isolator based on experimental Schlieren *** velocity field prediction model was designed with convolutional neural networks as the main *** experiments of a scramjet isolator under continuous Mach number variation were carried out,and Schlieren images of the flow field inside the isolator were *** simulations of the isolator were also carried out,and the velocity fields inside the isolator under various Mach numbers were *** velocity field prediction model was trained using flow field datasets containing experimental Schlieren images and velocity field,and the mapping relationship between the experimental Schlieren images and the predicted velocity field was successfully established.

关键词： Data-driven model Deep learning Neural networks Scramjet isolator Velocity field prediction

Relationships among Sedentary Time,Electronic Product Addiction,and Depression in Adolescents during the COVID-19 Epidemic:A Cross-Lagged Study

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International Journal of Mental Health Promotion 2024年第3期26卷 221-228页

作者： Feng Sheng chen kong Chao Li Teaching Department of Sports Qufu Normal UniversityQufu273165China Teaching Department of Sports Shandong Management UniversityJinan250100China General Education Center Weifang Vocational CollegeWeifang262737China

Objective:This study was conducted to explore the relationships among sedentary behavior(SB),electronic product addiction(EPA),and depression(D)in adolescents during the COVID-19 ***:A total of 604 adolescents(including 309 girls and 295 boys aged 12-18)were selected from Qufu City,Shandong Province,China for three rounds of *** model was constructed using AMOS 23.0 software,and cross-lagged analysis was ***:SB at T1 can significantly positively predict SB and EPA at T2(p<0.05).EPA at T1 can significantly positively predict SB and D at T2(p<0.05).Physical activity level and SB at T2 can significantly predict SB and EPA at T3(p<0.05).EPA at T2 can significantly predict SB,EPA,and D at T3(p<0.05).Conclusions:SB and EPA are predictive factors for ***,SB can significantly positively predict D and indirectly predict D through the mediating effect of EPA.

关键词： COVID-19 electronic product addiction depression sedentary behavior

A Statistical Model for Phase Difference Spectrum of Ground-Motion and Its Application in Generating Non-Stationary Seismic Waves

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Computer Modeling in Engineering & Sciences 2020年第7期124卷 265-285页

作者： Dongsheng Du Sheng Shi Weizhi Xu chen kong Shuguang Wang Weiwei Li College of Civil Engineering Nanjing University of TechnologyNanjing210009China China Jiangsu International Group Architecture Design Institute Nanjing211816China

The intensity non-stationarity is one of the most important features of earthquake *** of this feature is significant to the generation of artificial earthquake *** on the theory of phase difference spectrum,an intensity non-stationary envelope function with log-normal form is *** a tremendous amount of earthquake records downloaded on Kik-net,a parameter fitting procedure using the genetic algorithm is conducted to obtain the value of model parameters under different magnitudes,epicenter distances and site conditions.A numerical example is presented to describe the procedure of generating fully non-stationary ground motions via spectral representation,and the mean EPSD(evolutionary power spectral density)of simulated waves is proved to agree well with the target *** results show that the proposed model is capable of describing the intensity non-stationary features of ground motions,and it can be used in structural anti-seismic analysis and ground motion simulation.

关键词： Intensity non-stationarity parameter fitting genetic algorithm phase

Current recognition and management of intra-abdominal hypertension and abdominal compartment syndrome among tertiary Chinese intensive care physicians

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2011年第2期12卷 156-162页

作者： Jian-cang ZHOU Hong-chen ZHAO kong-han PAN Qiu-ping XU Department of Critical Care Medicine Sir Run Run Shaw Hospital School of Medicine Zhejiang University Hangzhou 310016 China

This survey was designed to clarify the current understanding and clinical management of intra-abdominal hypertension （IAH）/abdominal compartment syndrome （ACS） among intensive care physicians in tertiary Chinese hospitals. A postal twenty-question questionnaire was sent to 141 physicians in different intensive care units （ICUs）. A total of 108 （76.6%） questionnaires were returned. Among these, three quarters worked in combined medical-surgical ICUs and nearly 80% had primary training in internal or emergency medicine. Average ICU beds, annual admission, ICU length of stay, acute physiology and chronic health evaluation （APACHE）II score, and mortality were 18.2 beds, 764.5 cases, 8.3 d, 19.4, and 21.1%, respectively. Of the respondents, 30.6% never measured intra-abdominal pressure （IAP）. Although the vast majority of the ICUs adopted the exclusively transvesicular method, the over- whelming majority （88.0%） only measured lAP when there was a clinical suspicion of IAH/ACS and only 29.3% measured either often or routinely. Moreover, 84.0% used the wrong priming saline volume while 88.0% zeroed at reference points which were not in consistence with the standard method for lAP monitoring recommended by the World Society of Abdominal Compartment Syndrome. ACS was suspected mainly when there was a distended ab- domen （92%）, worsening oliguria （80%）, and increased ventilatory support requirement （68%）. Common causes for IAH/ACS were ＂third-spacing from massive volume resuscitation in different settings＂（88%）, ＂intra-abdominal bleeding＂, and ＂liver failure with ascites＂（52% for both）. Though 60% respondents would recommend surgical decompression when the lAP exceeded 25 mmHg, accompanied by signs of organ dysfunction, nearly three quarters of re- spondents preferred diuresis and dialysis. A total of 68% of respondents would recommend paracentesis in the treatment for ACS. In conclusion, urgent systematic education is absolutely necessary for most intensive care physician

关键词： Questionnaire Intra-abdominal pressure Intra-abdominal hypertension Decompression laparotomy Abdominal compartment syndrome

A deep learning-based approach for flow field prediction in a dual-mode combustor

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Propulsion and Power Research 2024年第2期13卷 178-193页

作者： chen kong Ziao Wang Fuxu Quan Yunfei Li Juntao Chang Harbin Institute of Technology Harbin 150001China

Accurate acquisition of the distribution offlow parameters inside the supersonic combustor is of great significance for hypersonicflight *** is an interesting attempt to introduce a data-driven model to a supersonic combustor forflowfield *** paper proposes a novel method for predicting theflowfield in a dual-mode *** prediction convolutional neural network with multiple branches is *** investiga-tions for a strut variable geometry combustor have been conducted to obtainflowfield data for training the network as aflowfield prediction *** data are obtained by changing the equivalent ratio,incomingflow condition and geometry of the supersonic *** Mach number distribution can be obtained from the trainedflowfield prediction model using the combustor wall pressure as input with high *** accuracy offlowfield prediction is discussed in several ***,the combustion mode detection is im-plemented on the predictionflowfield.

关键词： Flowfield prediction Deep learning(DL) Convolutional neural networks(CNNs) Data-driven model Dual-mode combustor Variable geometry combustor

DETECTION AND ANALYSIS OF WELD POOL SHAPE FOR CO_2 SHORT CIRCUITING ARC WELDING

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Chinese Journal of Mechanical Engineering 2001年第3期14卷 282-285页

作者： Sun Zhenguo,Wang Junbo,chen Qiang,kong Wende (Department of Mechanical Engineering, Qinghua University) 清华大学机械工程系北京

A general industrial CCD( ICCD) camera is redesigned to detect the weld pool without arc at the period of short circuiting, so that the interference of arc and spatter during CO2 short circuiting arc welding is eliminated. Through the analysis of weld pool image, both size parameters (such as weld pool area A, weld pool length L1, L2 and weld pool breadth b) and contour parameters (b, which describe the curves of weld pool boundany) ,which could indicate the shape features of weld pool, had been defined to express weld pool information quantitatively. The investigation of the relationships between weld pool shape parameters and welding process parameters may be beneficial to the quality control of CO2 welding.

关键词： ICCD camera Pool image CO2 short circuiting arc welding

Enhanced cyclic stability of partially disordered spinel cathodes through direct fluorination with gaseous fluorine

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Rare Metals 2024年第4期43卷 1635-1646页

作者： Yong-Nian Ma Ling-chen kong Shao-Shan chen Yong Wang Li-Dong Sun Cong Peng Meng-Meng Qin Yu Li Wei Feng Tianjin Key Laboratory of Composite and Functional Materials School of Materials Science and EngineeringTianjin UniversityTianjin300072China Institute of Advanced Technology and Equipment Beijing University of Chemical TechnologyBeijing100029China

Spinel-type cathodes are considered an optimal substitute for conventional layered oxide cathodes owing to their use of inexpensive and earth-abundant manganese as the redox-active ***,the introduction of cation disorder can effectively suppress the detrimental two-phase reaction to realize high capacities in a wide voltage ***,the continuous capacity decay during cycles has hindered the widespread application of these cathode *** fluorides exhibit excellent electrochemical stability at high voltage;therefore,in this study,the direct F2 gas reaction with a partially disordered spinel cathode(Li_(1.6)Mn_(1.6)O_(3.7)F_(0.3,)LMOF1.6)was initially applied to investigate the impacts of fluorination on the surface structure and electrochemical *** inorganic fluorinated layer,mainly containing LiF,was distributed uniformly on the surface of LMOF1.6nanoparticles after fluorination for an appropriate time without the turbulence caused by the valency of manganese cation,which improved the capacity retention and rate capability by the suppression of structural damage,parasitic reaction,and cation *** LMOF1.6cathode fluorinated for 0.5 h exhibited a capacity of283.6 mAh·g^(-1)at 50 mA·g^(-1)and an enhanced capacity retention of 29.6%after 50 cycles in the voltage range of1.5-4.8 V,as compared to the pristine LMOF1.6 with only27.9%capacity retention.

关键词： Spinel-type cathodes Direct fluorination Capacity retention ability High rate capability

Sparse and Low-Rank Covariance Matrix Estimation

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Journal of the Operations Research Society of China 2015年第2期3卷 231-250页

作者： Sheng-Long Zhou Nai-Hua Xiu Zi-Yan Luo Ling-chen kong Department of Applied Mathematics Beijing Jiaotong UniversityBeijing 100044China State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong UniversityBeijing 100044China

This paper aims at achieving a simultaneously sparse and low-rank estimator from the semidefinite population covariance *** first benefit from a convex optimization which develops l1-norm penalty to encourage the sparsity and nuclear norm to favor the low-rank *** the proposed estimator,we then prove that with high probability,the Frobenius norm of the estimation rate can be of order O(√((slgg p)/n))under a mild case,where s and p denote the number of nonzero entries and the dimension of the population covariance,respectively and n notes the sample ***,an efficient alternating direction method of multipliers with global convergence is proposed to tackle this problem,and merits of the approach are also illustrated by practicing numerical simulations.

关键词： Covariance matrix Sparse and low-rank estimator Estimation rate Alternating direction method of multipliers