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Analytic Initial Relative Orbit Solution for Angles-Only Space Rendezvous Using Hybrid Dynamics Method

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Computer Modeling in Engineering & Sciences 2020年第1期122卷 221-234页

作者： Baichun Gong Shuang Li lili zheng Jinglang Feng Nanjing University of Aeronautics and Astronautics Nanjing210016China Beijing Institute of Aerospace System Engineering Beijing100076China University of Strathclyde GlasgowG11XQScotland

A closed-form solution to the angles-only initial relative orbit determination(IROD)problem for space rendezvous with non-cooperated target is developed,where a method of hybrid dynamics with the concept of virtual formation is introduced to analytically solve the *** is placed on developing the solution based on hybrid dynamics(i.e.,Clohessy-Wiltshire equations and two-body dynamics),obtaining formation geometries that produce relative orbit state observability,and deriving the approximate analytic error covariance for the IROD solution.A standard Monte Carlo simulation system based on two-body dynamics is used to verify the feasibility and evaluate the performance proposed *** sensitivity of the solution accuracy to the formation geometry,observation numbers is presented and discussed.

关键词： Space rendezvous relative orbit determination angles-only measurement covariance analysis

Effects of High Temperature Oxidation on Mechanical Properties of Ti_3AlC_2

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Journal of Materials Science & Technology 2017年第6期33卷 596-602页

作者： Xichao Li lili zheng Yuhai Qian Jingjun Xu Meishuan Li Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences University of Chinese Academy of Sciences

The oxidation tests of Ti_3AlC_2 were conducted at 1100 and 1200？C in air for 48 and 360 h, respectively,and the effects of high temperature oxidation on the flexural strength and hardness of Ti_3AlC_2 were investigated. The microstructure, grain size and phase compositions of Ti_3AlC_2 substrate didn＇t change after oxidation, hence the oxide removed Ti_3AlC_2 substrate maintained its initial flexural strength and hardness. However, the flexural strength of oxide retained Ti_3AlC_2 decreased by about 5%. Acoustic emission monitoring indicated that during the process of three-point bending test, the formed Al_2O_3 scale on Ti_3AlC_2 surface fractured firstly in a cleavage manner, then the substrate/oxide interface cracked,and finally the Ti_3AlC_2 substrate fractured. The mechanical degradation was caused by the preferential formation of cracks in brittle Al_2O_3 scale as well as at defective and lacunose grain boundaries of the substrate where stress concentration generated. The mechanical degradation was insensitive to oxidation temperature and time in the present conditions. In addition, the surface hardness increased significantly after oxidation due to the formed hard Al_2O_3 scale on the surface of Ti_3AlC_2 substrate.

关键词： Ti3AlC2 Oxidation Flexural strength Hardness Bending test Acoustic emission

Study on oxygen transport and titanium oxidation in coating cracks under parallel gas flow based on LBM modelling

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Chinese Journal of Chemical Engineering 2023年第4期56卷 15-24页

作者： Shengfeng Luo Song Zhang Yiping Zeng Hui Zhang lili zheng Zhaopeng Xu Department of Engineering Physics Tsinghua UniversityBeijing 100084China Department of Mechanics and Aerospace Engineering Southern University of Science and TechnologyShenzhen 518055China Institute for Aero Engine Tsinghua UniversityBeijing 100084China Shenzhen Smart Hua Information Technology Research Co. Ltd.Shenzhen 518000China School of Aerospace Engineering Tsinghua UniversityBeijing 100084China Chinese Academy of Agricultural Mechanization Sciences Beijing 100084China

The oxygen transportation from surrounding air to coating cracks is an important factor in the oxidation and ignition of titanium alloy. In this work, the oxygen transport and surface oxidation of titanium in inclined cracks of coating under parallel airflow are studied with the lattice Boltzmann method(LBM).A boundary scheme of LBM about surface reaction is developed. The conversion factors are utilized to build the relationship between the physical scale and the lattice scale. The reliability of the LBM model is validated by the finite element method(FEM). The results show that the convective mass transport driven by the surrounding airflow and the vortex structure formed inside the crack are the two significant factors that influence the oxygen transport in cracks. The convective mass transfer plays a major role in oxygen transport when the inclination angle of the crack is small. For the cases with a large inclination angle, the oxygen transfer from the top to the bottom of the crack is mainly controlled by mass diffusion mechanism. The oxygen concentration in inclined cracks is generally less than that in vertical cracks, and oxidation and ignition of the substrate titanium might be more likely to occur in relatively vertical cracks.

关键词： Coating crack Oxidation Transport Ignition Numerical simulation

Effect of bovine serum albumin on the micellization of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymers in aqueous solutions by fluorescence spectroscopy

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Science China Chemistry 2006年第6期49卷 541-549页

作者： GUO Chen WANG Jing LIANG Xiangfeng zheng lili LIU Huizhou Laboratory of Separation Science and Engineering State Key Laboratory of Biochemical EngineeringInstitute of Process EngineeringGraduate University of Chinese Academy of SciencesBeijing 100080China

Effect of bovine serum albumin(BSA)on the temperature-dependent association behavior of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)(PEO-PPO-PEO)block copolymers was investigated using pyrene fluorescence *** critical micellization temperature(CMT)of pluronics in aqueous solution was increased by the addition of BSA.A closed association model was used to obtain the standard free energies(△DG^(0)),enthalpies(△DH^(0)),and entropies(△DS^(0))of *** standard enthalpy and entropy of micellization for pluronic polymers in water were decreased with an increase of the BSA *** more PPO component in the pluronic polymer,the higher the changed values of micellization enthalpy and *** hydrophobic part of the pluronics,PPO,was responsible for the interaction between pluronics and *** interaction between PPO and BSA was correlated to the alternation of the PPO-PPO interaction by the addition of BSA,which would shift the CMT toward higher temperature and alter the thermodynamic parameters of micellization for pluronics in aqueous solutions.

关键词： block copolymer bovine serum albumin micelle fluorescence spectroscopy.

Nitrogen addition inhibits total monoterpene emissions in subtropical forest floor of South China

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Soil Ecology Letters 2021年第1期3卷 63-72页

作者： Xingran Huang lili zheng Pingping Guo Zhigang Yi Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation College of Resources and EnvironmentFujian Agriculture and Forestry UniversityFuzhou 350002China Minjiang River Estuary Wetland National Nature Reserve Administrative Office Fuzhou 350002China

Monoterpenes(MTs)play crucial roles not only in atmospheric chemistry and global climate change but also in soil processes and soil *** nitrogen(N)deposition can influence soil microbial community and litter decomposition,and consequently alters MT fluxes from forest floors and ***,the responses of soil and litter MT to increased N deposition remain poorly understood and the influences of N addition are sometimes *** the present study,static chambers were placed in masson pine forest(PF)and in monsoon evergreen broad-leaf forest(BF)at Dinghushan,subtropical *** preconcentrator-GC–MS was used to analyze the effect of N addition on MT fluxes from the forest floors and *** results showed that under control treatment(without N addition),the total MT emission rates were 279.90±137.17 and 102.70±45.36 pmol m^(–2)s^(–1) in the PF and BF floors,respectively,withα-pinene being the largest MT species in the PF and limonene in the BF.α-pinene andβ-pinene emission rates decreased significantly in both forest floors after N addition,whereas a diverse trend was found for limonene and camphene in the PF ***,some MT fluxes showed significant negative correlations with soil respiration and soil *** was important in MT fluxes from forest floors and its emission rates were enhanced by N ***,different MT response to elevated N was found between the forest floor and *** study indicated that the elevated N deposition in the future would inhibit the MT emissions from the subtropical forest floor.

关键词： Biogenic volatile organic compounds Dinghushan Biosphere Reserve Forest floor Little Monoterpene Nitrogen deposition

Angles-only initial relative orbit determination algorithm for noncooperative spacecraft proximity operations

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Astrodynamics 2018年第3期2卷 217-231页

作者： Baichun Gong Wendan Li Shuang Li Weihua Ma lili zheng Advanced Space Technology Nanjing University of Aeronautics and AstronauticsNanjing210016China National Key Laboratory of Aerospace Flight Dynamics Northwestern Polytechnical UniversityXi’an 710072China Beijing Institute of Aerospace System Engineering Beijing 100076China

This research furthers the development of a closed-form solution to the angles-only initial relative orbit determination problem for non-cooperative target close-in proximity operations when the camera offset from the vehicle center-of-mass allows for range *** previous work,the solution to this problem had been shown to be non-global optimal in the sense of least square and had only been discussed in the context of Clohessy–*** this paper,the emphasis is placed on developing a more compact and improved solution to the problem by using state augmentation least square method in the context of the Clohessy–Wiltshire and Tschauner–Hempel dynamics,derivation of corresponding error covariance,and performance analysis for typical rendezvous missions.A two-body Monte Carlo simulation system is used to evaluate the performance of the *** sensitivity of the solution accuracy to camera offset,observation period,and the number of observations are presented and discussed.

关键词： initial relative orbit determination angles-only navigation proximity operations rendezvous

High-altitude tree growth responses to climate change across the Hindu Kush Himalaya

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Journal of Plant Ecology 2021年第5期14卷 829-842页

作者： lili zheng Narayan Prasad Gaire Peili Shi Lhasa Plateau Ecosystem Research Station Key Laboratory of Ecosystem Network Observation and ModelingInstitute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China College of Resources and Environment University of Chinese Academy of SciencesBeijing 100190China CAS Key Laboratory of Tropical Forest Ecology Xishuanghanna Tropical Botanical GardenChinese Academy of SciencesMenglunMenglaYunnan 666303China Central Department of Environmental Science Tribhuvan UniversityKirtipurKathniantluNepal

Aims Rapid warming at high altitudes may lead to a higher sensitivity in tree growth to *** key factors constraining tree radial growth and to what extent regional tree growth has suffered from climatic changes are *** Tree-ring width data were collected from 73 sites across the Hindu Kush Himalaya(HKH),including three dominant genera(Abies,Juniperus and Picea)at high altitudes over 3000 *** time warping was introduced to develop subregional chronologies by considering the synchrony of annual tree growth among different *** quantified the contribution of the climate variables,and analyzed the spatiotemporal variation of the growth–climate *** Findings The site chronologies were grouped into three clusters,corresponding to the three distinct bioclimatic zones,*** western HKH,central-eastern HKH and southeastern Tibetan Plateau(TP).Tree growth was positively correlated to winter and spring precipitation in the drier western HKH,and to winter temperature and spring precipitation in the humid southeastern *** growth was markedly constrained by the minimum temperature,especially in winter,with its importance increasing from the west toward the *** shown by moving correlation analysis,the signal of winter temperature in tree growth was weakened in the western and central-eastern HKH,while it was enhanced in the southeastern TP following rapid warming since the *** results highlight that continuous warming may cause forest recession due to warming-induced moisture deficit in the western HKH,but forest expansion in the southeastern TP.

关键词： tree ring high-altitude forests key climate factors tree growth-climate relationships growth trends climate sensitivity

In-depth analysis of the genome of Trypanosoma evansi, an etiologic agent of surra

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Science China(Life Sciences) 2019年第3期62卷 406-419页

作者： lili zheng Ning Jiang Xiaoyu Sang Naiwen Zhang Kai Zhang Hongyu Chen Na Yang Ying Feng Ran Chen Xun Suo Qijun Chen Key Laboratory of Zoonosis College of Animal Science and Veterinary Medicine Shenyang Agricultural University Department of Food Science Shenyang Agricultural University Department of Parasitology College of Veterinary Medicine Chinese Agricultural University

Trypanosoma evansi is the causative agent of the animal trypanosomiasis surra, a disease with serious economic burden worldwide. The availability of the genome of its closely related parasite Trypanosoma brucei allows us to compare their genetic and evolutionarily shared and distinct biological features. The complete genomic sequence of the T. evansi YNB strain was obtained using a combination of genomic and transcriptomic sequencing, de novo assembly, and bioinformatic analysis. The genome size of the T. evansi YNB strain was 35.2 Mb, showing 96.59% similarity in sequence and 88.97% in scaffold alignment with T. brucei. A total of 8,617 protein-coding genes, accounting for 31% of the genome, were predicted. Approximately 1,641 alternative splicing events of 820 genes were identified, with a majority mediated by intron retention, which represented a major difference in post-transcriptional regulation between T. evansi and T. brucei. Disparities in gene copy number of the variant surface glycoprotein, expression site-associated genes, microRNAs, and RNA-binding protein were clearly observed between the two parasites. The results revealed the genomic determinants of T. evansi, which encoded specific biological characteristics that distinguished them from other related trypanosome species.

关键词： Trypanosoma trypanosomiasis genome annotation function

Noninvasive Assessment of Liver Fibrosis and Inflammation in Chronic Hepatitis B:A Dual-task Convolutional Neural Network(DtCNN)Model Based on Ultrasound Shear Wave Elastography

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Journal of Clinical and Translational Hepatology 2022年第6期10卷 1077-1085页

作者： Chengyan Wang lili zheng Yan Li Shujun Xia Jun Lv Xumei Hu Weiwei Zhan Fuhua Yan Ruokun Li Xinping Ren Human Phenome Institute Fudan UniversityShanghaiChina Ultrasound Department Ruijin Hospital Wuxi BranchShanghai Jiao Tong University School of MedicineWuxiJiangsuChina Department of Radiology Ruijin HospitalShang-hai Jiao Tong University School of MedicineShanghaiChina Ultrasound Department Ruijin HospitalShanghai Jiao Tong University School of MedicineShanghaiChina School of Computer and Control Engineering Yantai UniversityYantaiShandongChina

Background and Aims:Liver stiffness(LS)measured by shear wave elastography(SWE)is often influenced by hepat-ic *** aim was to develop a dual-task convo-lutional neural network(DtCNN)model for the simultaneous staging of liver fibrosis and inflammation activity using ***:A total of 532 patients with chronic hepatitis B(CHB)were included to develop and validate the DtCNN *** additional 180 consecutive patients between De-cember 2019 and April 2021 were prospectively included for further *** patients underwent 2D-SWE examina-tion and serum biomarker assessment.A DtCNN model con-taining two pathways for the staging of fibrosis and inflam-mation was used to improve the classification of significant fibrosis(≥F2),advanced fibrosis(≥F3)as well as cirrhosis(F4).Results:Both fibrosis and inflammation affected LS measurements by *** proposed DtCNN performed the best among all the classification models for fibrosis stage[significant fibrosis AUC=0.89(95%CI:0.87-0.92),ad-vanced fibrosis AUC=0.87(95%CI:0.84-0.90),liver cirrho-sis AUC=0.85(95%CI:0.81-0.89)].The DtCNN-based pre-diction of inflammation activity achieved AUCs of 0.82(95%CI:0.78-0.86)for grade≥A1,0.88(95%CI:0.85-0.90)grade≥A2 and 0.78(95%CI:0.75-0.81)for grade≥A3,which were significantly higher than the AUCs of the single-task *** findings were observed in the prospec-tive ***:The proposed DtCNN improved di-agnostic performance compared with existing fibrosis staging models by including inflammation in the model,which sup-ports its potential clinical application.

关键词： Fibrosis Inflammation Shear wave elastography Chronic hepati-tis B Dual-task convolutional neural network.