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Static aeroelastic analysis including geometric nonlinearities based on reduced order model

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Chinese Journal of Aeronautics 2017年第2期30卷 638-650页

作者： xie Changchuan An chao Liu yi Yang chao School of Aeronautic Science and Engineering Beihang University Beijing 100083 China

This paper describes a method proposed for modeling large deflection of aircraft in nonlinear aeroelastic analysis by developing reduced order model（ROM）.The method is applied for solving the static aeroelastic and static aeroelastic trim problems of flexible aircraft containing geometric nonlinearities;meanwhile,the non-planar effects of aerodynamics and follower force effect have been considered.ROMs are computational inexpensive mathematical representations compared to traditional nonlinear finite element method（FEM） especially in aeroelastic solutions.The approach for structure modeling presented here is on the basis of combined modal/finite element（MFE） method that characterizes the stiffness nonlinearities and we apply that structure modeling method as ROM to aeroelastic analysis.Moreover,the non-planar aerodynamic force is computed by the non-planar vortex lattice method（VLM）.Structure and aerodynamics can be coupled with the surface spline method.The results show that both of the static aeroelastic analysis and trim analysis of aircraft based on structure ROM can achieve a good agreement compared to analysis based on the FEM and experimental result.

关键词： Aeroelasticity Finite element method Geometric nonlinearity Reduced order models Trims

Nano-sized zinc addition enhanced mammary zinc translocation without altering health status of dairy cows

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Animal Nutrition 2021年第4期7卷 1024-1030页

作者： Jie Cai chao Miao yi Chen Yunyi xie Jianxin Liu Diming Wang Key Laboratory of Molecular Animal Nutrition of Ministry of Agriculture College of Animal SciencesInstitute of Dairy ScienceZhejiang UniversityHangzhou 310058China

This study aimed to evaluate role of nano-sized zinc(Zn)on lactation performance,health status,and mammary permeability of lactating dairy cows.Thirty multiparous dairy cows with similar days in milk(158±43.2)and body weight(694±60.5 kg)were chosen based on parity and milk production and were randomly assigned to 3 treatment groups:basal diet(control,69.6 mg/kg of Zn adequate in Zn requirement),basal diet additional Zn-methionine(Zn-Met,providing 40 mg/kg of Zn),and basal diet additional nano-sized Zn oxide(nZnO,providing 40 mg/kg of Zn).The study lasted for 10 wk,with the first 2 wk as adaptation.Feed intake,milk yield and the related variables,and plasma variables were determined every other week.Blood hematological profiles were determined in the 8 th week of the study.We found that feed intake,milk yield,and milk composition were similar across the 3 groups.The nZnO-and Zn-Met-fed cows had greater milk Zn concentrations in the milk(3.89 mg/L(Zn-Met)and3.93 mg/L(nZnO))and plasma(1.25 mg/L(Zn-Met)and 1.29 mg/L(nZnO))than the control cows(3.79 mg/L in milk and 1.21 mg/L in plasma).The nZnO-fed cows had higher Zn concentrations in plasma but not in milk compared to Zn-Met-fed cows.The Zn appearance in milk was greater in nZnO-fed(area under curve during the first 4 h post-feeding for milk Zn:16.1 mg/L)and Zn-Met-fed cows(15.7 mg/L)than in control cows(15.0 mg/L).During the first 4 h post-feeding,milk to blood Zn ratio was greater in nZnO-fed animals but lower in Zn-Met-fed cows compared with control cows.Oxidative stress-related variables in plasma,blood hematological profiles,and mammary permeability related variables were not different across treatments.In summary,lactation performance,Zn concentrations in milk and plasma,hematological profiles,mammary permeability were similar in cows fed nZnO and Zn-Met.We therefore suggested that nZnO feeding can improve Zn bioavailability without impairing lactation performance,health status,and mammary gland permeability in dairy cows.

关键词： Zinc Nano-size Oxidative stress Lactation performance Mammary gland permeability

Gust response analysis and wind tunnel test for a high-aspect ratio wing

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Chinese Journal of Aeronautics 2016年第1期29卷 91-103页

作者： Liu yi xie Changchuan Yang chao Cheng Jialin School of Aeronautic Science and Engineering Beihang UniversityBeijing 100083China Chengdu Aircraft Industrial(Group)Co.Ltd. Chengdu 610073China

A theoretical nonlinear aeroelastic response analysis for a flexible high-aspect ratio wing excited by harmonic gust load is presented along with a companion wind tunnel test. A multidisci- plinary coupled numerical calculation is developed to simulate the flexible model wing undergoing gust load in the time domain via discrete nonlinear finite element structural dynamic analysis and nonplanar unsteady vortex lattice aerodynamic computation. A dynamic perturbation analysis about a nonlinear static equilibrium is also used to determine the small perturbation flutter bound- ary. A novel noncontact 3-D camera measurement analysis system is firstly used in the wind tunnel test to obtain the spatial large deformation and responses. The responses of the flexible wing under different static equilibrium states and frequency gust loads are discussed. The fair to good quanti- tative agreements between the theoretical and experimental results demonstrate that the presented analysis method is an acceptable way to predict the geometrically nonlinear gust response for flex- ible wings.

关键词： Gust loads High-aspect ratio wing Nonlinear analysis Unsteady vortex latticemethod （UVLM） Wind tunnels

Static aeroelastic analysis of very flexible wings based on non-planar vortex lattice method

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Chinese Journal of Aeronautics 2013年第3期26卷 514-521页

作者： xie Changchuan Wang Libo Yang chao Liu yi School of Aeronautic Science and Engineering Beihang University

A rapid and efficient method for static aeroelastic analysis of a flexible slender wing when considering the structural geometric nonlinearity has been developed in this paper. A non-planar vortex lattice method herein is used to compute the non-planar aerodynamics of flexible wings with large deformation. The finite element method is introduced for structural nonlinear statics analysis. The surface spline method is used for structure/aerodynamics coupling. The static aeroelastic characteristics of the wind tunnel model of a flexible wing are studied by the nonlinear method presented, and the nonlinear method is also evaluated by comparing the results with those obtained from two other methods and the wind tunnel test. The results indicate that the traditional linear method of static aeroelastic analysis is not applicable for cases with large deformation because it produces results that are not realistic. However, the nonlinear methodology, which involves combining the structure finite element method with the non-planar vortex lattice method, could be used to solve the aeroelastic deformation with considerable accuracy, which is in fair agreement with the test results. Moreover, the nonlinear finite element method could consider complex structures. The non-planar vortex lattice method has advantages in both the computational accuracy and efficiency. Consequently, the nonlinear method presented is suitable for the rapid and efficient analysis requirements of engineering practice. It could be used in the preliminary stage and also in the detailed stage of aircraft design.

关键词： Aeroelasticity Geometric nonlinearity Non-planar aerodynamics Static aeroelasticity Vortex lattice method

Artificial intelligence computed tomography helps evaluate the severity of COVID-19 patients:A retrospective study

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World Journal of Emergency Medicine 2022年第2期13卷 91-97页

作者： yi Han Su-cheng Mu Hai-dong Zhang Wei Wei Xing-yue Wu chao-yuan Jin Guo-rong Gu Bao-jun xie chao-yang Tong Department of Emergency Medicine Zhongshan Hospital Fudan UniversityShanghai 200032China Department of Radiology Renmin Hospital of Wuhan UniversityWuhan 430060China

BACKGROUND:Computed tomography(CT)is a noninvasive imaging approach to assist the early diagnosis of pneumonia.However,coronavirus disease 2019(COVID-19)shares similar imaging features with other types of pneumonia,which makes differential diagnosis problematic.Artificial intelligence(AI)has been proven successful in the medical imaging field,which has helped disease identification.However,whether AI can be used to identify the severity of COVID-19 is still underdetermined.METHODS:Data were extracted from 140 patients with confirmed COVID-19.The severity of COVID-19 patients(severe vs.non-severe)was defined at admission,according to American Thoracic Society(ATS)guidelines for community-acquired pneumonia(CAP).The AI-CT rating system constructed by Hangzhou yiTU Healthcare Technology Co.,Ltd.was used as the analysis tool to analyze chest CT images.RESULTS:A total of 117 diagnosed cases were enrolled,with 40 severe cases and 77 non-severe cases.Severe patients had more dyspnea symptoms on admission(12 vs.3),higher acute physiology and chronic health evaluation(APACHE)II(9 vs.4)and sequential organ failure assessment(SOFA)(3 vs.1)scores,as well as higher CT semiquantitative rating scores(4 vs.1)and AI-CT rating scores than non-severe patients(P<0.001).The AI-CT score was more predictive of the severity of COVID-19(AUC=0.929),and ground-glass opacity(GGO)was more predictive of further intubation and mechanical ventilation(AUC=0.836).Furthermore,the CT semiquantitative score was linearly associated with the AI-CT rating system(Adj R2=75.5%,P<0.001).CONCLUSIONS:AI technology could be used to evaluate disease severity in COVID-19 patients.Although it could not be considered an independent factor,there was no doubt that GGOs displayed more predictive value for further mechanical ventilation.

关键词： COVID-19 Artificial intelligence Chest computed tomography

A further investigation to mechanism of the electrorheological effect of waxy oils:Behaviors of charged particles under electric field

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Petroleum Science 2023年第2期20卷 1247-1254页

作者： yi-Wei xie Hong-ying Li chao-Yue Zhang Yang Su Qian Huang Feng Jiang chao-Hui Chen Shan-Peng Han Jin-Jun Zhang National Engineering Research Center of Oil and Gas Pipeline Transportation Safety China University of PetroleumBeijing 102249China MOE Key Laboratory of Petroleum Engineering China University of PetroleumBeijing 102249China Beijing Key Laboratory of Urban Oil&Gas Distribution Technology China University of PetroleumBeijing 102249China PetroChina Planning and Engineering Institute Beijing 100083China

Exposing waxy oils to an electric field may significantly improve their cold flowability.Our previous study has shown that interfacial polarization,i.e.,charged particle accumulation on the wax particle surface,is the primary mechanism of the electrorheological behavior of waxy oils.However,the way that charged particles interact with wax particles under an electric field remains unknown.In this study,we found no viscosity and impedance change for two waxy crude oils after their exposure to a high-voltage electric field.However,the yield stresses were reduced obviously.We thus proposed that the collision of colloidal particles such as resins and asphaltenes with the wax particles could be an essential mechanism that the wax particle structure was weakened.To verify this hypothesis,a series of ad hoc experiments were carried out,i.e.,by performing electrorheological tests on model waxy oils containing additives removable under an electric field,including electrically-neutral colloidal particles(Fe3O4),charged colloidal particles(resins),and oil-soluble electrolyte(C22H14CoO4),respectively,and demonstrated that upon application of a high-voltage electric field,charged particles in a waxy oil may move and thus collide with wax particles,and consequently adhere to the wax particle surface.The particle collision results in damage to the wax particle network,and the electrostatic repulsion arising from the adhesion of the charged particle on the wax particle diminishes attraction between wax particles.This study clarifies the process of interfacial polarization.

关键词： Waxy oil Electrorheological effect Interfacial polarization Charged particle motion

Detection of maize tassels for UAV remote sensing image with an improved YOLOX Model

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Journal of Integrative Agriculture 2023年第6期22卷 1671-1683页

作者： SONG chao-yu ZHANG Fan LI Jian-sheng xie Jin-yi YANG Chen ZHOU Hang ZHANG Jun-xiong College of Engineering China Agricultural UniversityBeijing 100083P.R.China College of Agronomy and Biotechnology China Agricultural UniversityBeijing 100083P.R.China

Maize tassel detection is essential for future agronomic management in maize planting and breeding,with application in yield estimation,growth monitoring,intelligent picking,and disease detection.However,detecting maize tassels in the field poses prominent challenges as they are often obscured by widespread occlusions and differ in size and morphological color at different growth stages.This study proposes the SEYOLOX-tiny Model that more accurately and robustly detects maize tassels in the field.Firstly,the data acquisition method ensures the balance between the image quality and image acquisition efficiency and obtains maize tassel images from different periods to enrich the dataset by unmanned aerial vehicle(UAV).Moreover,the robust detection network extends YOLOX by embedding an attention mechanism to realize the extraction of critical features and suppressing the noise caused by adverse factors(e.g.,occlusions and overlaps),which could be more suitable and robust for operation in complex natural environments.Experimental results verify the research hypothesis and show a mean average precision(mAP_(@0.5)) of 95.0%.The mAP_(@0.5),mAP_(@0.5-0.95),mAP_(@0.5-0.95(area=small)),and mAP_(@0.5-0.95(area=medium)) average values increased by 1.5,1.8,5.3,and 1.7%,respectively,compared to the original model.The proposed method can effectively meet the precision and robustness requirements of the vision system in maize tassel detection.

关键词： maize tassel detection remote sensing deep learning attention mechanism

Sintering kinetics involving grain growth and densification of Mg-PSZ nanopowders

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Journal of Iron and Steel Research(International) 2022年第7期29卷 1138-1144页

作者： yi-ming She Jie-fu Lang Di An chao-wei Si Xu-dong Luo Zhi-peng xie Jie-gang You School of Materials and Metallurgy University of Science and Technology LiaoningAnshan 114051LiaoningChina Institute of Advanced Structures Beijing Institute of TechnologyBeijing 100081China State Key Lab of New Ceramics and Fine Processing School of Materials Science and EngineeringTsinghua UniversityBeijing 100084China

Sintering kinetics have been found to be effective in judging the evolution of ceramics.By using magnesium oxide-partially stabilized zirconia(Mg-PSZ)powder prepared by co-precipitation as raw materials,the evolution of densification and grain growth for Mg-PSZ ceramics were investigated.The results indicated that the densification of samples was mainly controlled by grain boundary diffusion in intermediate sintering stage.During the sintering process,the grain growth mechanisms included normal grain growth,abnormal grain growth and solid solution drag-controlled grain growth.Interestingly,the apparent activation energy for grain growth of Mg-PSZ ceramics is lower than that of ZrO_(2)–Y_(2)O_(3)ceramics in the solid solution drag-controlled grain grow process,which will cause grain to grow easily.The sintering kinetics and microstructure of Mg-PSZ ceramics were studied,and the kinetic equation of grain growth at different temperatures was established.The results show that the strength difference between Mg-PSZ and yttrium oxide-stabilized zirconia is closely related to the easy grain growth of Mg-PSZ ceramics.

关键词： Magnesium oxide-partially stabilized zirconia Sintering kinetics Grain growth mechanism Densification mechanism Sizing nozzle

Prolonged Viral Shedding in Three Young Adult Cases of COVID-19

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Infectious Diseases & Immunity 2022年第4期2卷 289-292页

作者： Wen-yi Dong Ming-Ju Zhou Lei Huang chao Zhang Fu-Sheng Wang Zhou-Hua xie Guangxi AIDS Clinical Treatment Centre The Fourth People’s Hospital of NanningNanning 530013China Beijing Ditan Hospital Capital Medical UniversityBeijing 100015China Medical Department of Infectious Diseases The Fifth Medical Centre of Chinese PLA General HospitalNational Clinical Research Centre for Infectious DiseasesBeijing 100039China

Severe acute respiratory syndrome coronavirus-2 infection is usually self-limited,with a short duration for viral shedding within several weeks.However,prolonged viral shedding has been observed in severe or immune-compromised coronavirus disease 2019(COVID-19)cases.Here,we reported that three young adult cases of COVID-19 patients,who were either immunosuppressed nor severe,showed prolonged viral RNA shedding from the upper respiratory tract for 58,81,and 137 days since initial diagnosis.To our knowledge,this is the longest duration of viral shedding reported to date in young adult patients.Further studies on factors relevant to prolonged viral positivity,as well as the correlation between viral positivity and transmission risk are needed for the optimal management of COVID-19 patients with prolonged nucleic acid positive.

关键词： COVID-19 Immune-competent Prolonged viral shedding SAR-CoV-2