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The symmetric space,strong isotropy irreducibility and equigeodesic properties

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Science China Mathematics 2024年第1期67卷 129-148页

作者： Ming xu Ju tan School of Mathematical Sciences Capital Normal UniversityBeijing 100048China School of Microelectronics and Data Science Anhui University of TechnologyMa'anshan 243032China

A smooth curve on a homogeneous manifold G/H is called a Riemannian equigeodesic if it is a homogeneous geodesic for any G-invariant Riemannian metric.The homogeneous manifold G/H is called Riemannian equigeodesic,if for any x∈G/H and any nonzero y∈Tx(G/H),there exists a Riemannian equigeodesic c(t) with c(0)=x and ■(0)=y.These two notions can be naturally transferred to the Finsler setting,which provides the definitions for Finsler equigeodesics and Finsler equigeodesic spaces.We prove two classification theorems for Riemannian equigeodesic spaces and Finsler equigeodesic spaces,respectively.Firstly,a homogeneous manifold G/H with a connected simply connected quasi compact G and a connected H is Riemannian equigeodesic if and only if it can be decomposed as a product of Euclidean factors and compact strongly isotropy irreducible factors.Secondly,a homogeneous manifold G/H with a compact semisimple G is Finsler equigeodesic if and only if it can be locally decomposed as a product,in which each factor is Spin(7)/G2,G2/SU (3) or a symmetric space of compact type.These results imply that the symmetric space and the strongly isotropy irreducible space of compact type can be interpreted by equigeodesic properties.As an application,we classify the homogeneous manifold G/H with a compact semisimple G such that all the G-invariant Finsler metrics on G/H are Berwald.It suggests a new project in homogeneous Finsler geometry,i.e.,to systematically study the homogeneous manifold G/H on which all the G-invariant Finsler metrics satisfy a certain geometric property.

关键词： equigeodesic equigeodesic space flag manifold orbit type stratification symmetric space strongly isotropy irreducible space

Harnessing Interactional Sensory Genes for Rationally Reprogramming Chaotic Metabolism

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Research 2023年第3期2022卷 295-308页

作者： Chunlin tan Ping xu Fei Tao State Key Laboratory of Microbial Metabolism Joint International Research Laboratory of Metabolic and Developmental Sciencesand School of Life Sciences and BiotechnologyShanghai Jiao Tong UniversityShanghaiChina

Rationally controlling cellular metabolism is of great importance but challenging owing to its highly complex and chaotic nature.Natural existing sensory proteins like histidine kinases(HKs)are understood as“sensitive nodes”of biological networks that can trigger disruptive metabolic reprogramming(MRP)upon perceiving environmental fluctuation.Here,the“sensitive node”genes were adopted to devise a global MRP platform consisting of a CRISPR interference-mediated dual-gene combinational knockdown toolbox and survivorship-based metabolic interaction decoding algorithm.The platform allows users to decode the interfering effects of n×n gene pairs while only requiring the synthesis of n pairs of primers.A total of 35 HK genes and 24 glycine metabolic genes were selected as the targets to determine the effectiveness of our platform in a Vibrio sp.FA2.The platform was applied to decode the interfering impact of HKs on antibiotic resistance in strain FA2.A pattern of combined knockdown of HK genes(sasA_8 and 04288)was demonstrated to be capable of reducing antibiotic resistance of Vibrio by 108-fold.Patterns of combined knockdown of glycine pathway genes(e.g.,gcvT and ltaE)and several HK genes(e.g.,cpxA and btsS)were also revealed to increase glycine production.Our platform may enable an efficient and rational approach for global MRP based on the elucidation of high-order gene interactions.A web-based 1-stop service(https://***)is also provided to simplify the implementation of this smart strategy in a broad range of cells.

关键词： metabolism Rational programming

Genome-wide evolution analysis reveals low CpG contents of fast-evolving genes and identifies antiviral microRNAs

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Journal of Genetics and Genomics 2020年第1期47卷 49-60页

作者： Wenhong Zu Hang Zhang xun Lan Xu tan MOE Key Laboratory of Bioorganic Phosphorus Chemistry&Chemical Biology School of Pharmaceutical SciencesTsinghua UniversityBeijing100084China Beijing Advanced Innovation Center for Structural Biology.Beijing Frontier Research Center for Biological Structures Tsinghua UniversityBeijing100084China Department of Basic Medical Sciences School of MedicineTsinghua UniversityBeijing100084China Center for Infectious Disease Research Tsinghua UniversityBeijing100084China Tsinghua-Peking Center for Life Sciences Beijing100084China

Noncoding RNAs(ncRNAs) play important roles in many biological processes and provide materials for evolutionary adaptations beyond protein-coding genes, such as in the arms race between the host and pathogen. However, currently, a comprehensive high-resolution analysis of primate genomes that includes the latest annotated ncRNAs is not available. Here, we developed a computational pipeline to estimate the selections that act on noncoding regions based on comparisons with a large number of reference sequences in introns adjacent to the interested regions. Our method yields result comparable with those of the established codon-based method and phyloP method for coding genes;thus, it provides a holistic framework for estimating the selection on the entire genome. We further showed that fastevolving protein-coding genes and their corresponding 50 UTRs have a significantly lower frequency of the CpG dinucleotides than those evolving at an average pace, and these fast-evolving genes are enriched in the process of immunity and host defense. We also identified fast-evolving miRNAs with antiviral functions in cells. Our results provide a resource for high-resolution evolution analysis of the primate genomes.

关键词： Host-virus interaction Positive selection CpG dinucleotide Noncoding RNA MicroRNA

Improvements in the GRAPES-TCM and the forecast performance analysis in 2019

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Frontiers of Earth Science 2022年第1期16卷 144-157页

作者： Yan tan xu ZHANG Xiaolin xu Wei HUANG Shanghai Typhoon Institute China Meteorological AdministrationShanghai 200030China Key Laboratory of Numerical Modeling for Tropical Cyclone China Meteorological AdministrationShanghai 200030China Center of Ecological Meteorology and Satellite Remote Sensing Shanghai 200030China

In 2019,the operational Global Regional Assimilation and Prediction System-Tropical Cyclone Model(GRAPES-TCM)was updated by adopting the characteristic parameters in the official real-time released TC data of CMA,introducing the horizontal sixth-order diffusion scheme and adjusting the operational flowchart.In the case of the Super Typhoon Lekima,the model exhibits a reliable prediction ability for the type of tropical cyclone(TC)with northwestern tracking.The track and intensity forecasts in 2019 are significantly better than those over the past five years on average.The updated model can provide a skillful forecast of landfall position and rapid weakening process.Moreover,the precipitation pattern is close to the observation.TC forecast in 2019 shows that the updated GRAPES-TCM has a smaller track error than that of the previous year,and the 24 h intensity forecasting ability is improved.

关键词： GRAPES-TCM vortex initialization numerical diffusion scheme performance analysis

Key technologies and development trends of the soft abrasive flow finishing method

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2023年第12期24卷 1043-1064页

作者： Yunfeng tan Yesha NI Weixin xu Yuanshen XIE Lin LI Dapeng tan Key Lab of E&M Ministry of Education&Zhejiang ProvinceZhejiang University of TechnologyHangzhou 310014China State Key Laboratory of Fluid Power and Mechatronic Systems Zhejiang UniversityHangzhou 310058China Collaborative Innovation Center of High-end Laser Manufacturing Equipment Zhejiang Province&Ministry of EducationHangzhou 310014China

This paper reviews recent developments of the soft abrasive flow finishing(SAF)method in constraint space.The multiphase fluid dynamics modeling,material removal mechanism,auxiliary strengthening finishing techniques,and observation of surface impact effects by abrasive particles and cavitation bubbles are presented in brief.Development prospects and challenges are given for four aspects:thin-walled curved surfaces,biomedical functions,electronic information,and precise optical components.

关键词： Soft abrasive flow finishing(SAF) Dynamic modeling Material removal mechanism Processing optimization Strengthening finishing control technology

Streaming Algorithms for Non-Submodular Maximizationon the Integer Lattice

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Tsinghua Science and Technology 2023年第5期28卷 888-895页

作者： Jingjing tan Yue Sun Yicheng xu Juan Zou School of Mathematics and Information Science Weifang UniversityWeifang 261061China Beijing Institute for Scientific and Engineering Computing Beijing University of TechnologyBeijing 100124China Shenzhen Institute of Advanced Technology Chinese Academy of SciencesShenzhen 518055China School of Mathematical Sciences Qufu Normal UniversityQufu 273165China

Many practical problems emphasize the importance of not only knowing whether an element is selectedbut also deciding to what extent it is selected,which imposes a challenge on submodule optimization.In this study,we consider the monotone,nondecreasing,and non-submodular maximization on the integer lattice with a cardinalityconstraint.We first design a two-pass streaming algorithm by refining the estimation interval of the optimal value.Foreach element,the algorithm not only decides whether to save the element but also gives the number of reservations.Then,we introduce the binary search as a subroutine to reduce the time complexity.Next,we obtain a one-passstreaming algorithm by dynamically updating the estimation interval of optimal value.Finally,we improve the memorycomplexity of this algorithm.

关键词： integer lattice non-submodular streaming algorithm cardinality constraint

Probing microstructural evolution in weld metals subjected to varied CaF_(2)-TiO_(2) flux cored wires under high heat input electro-gas welding

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Journal of Iron and Steel Research(International) 2023年第1期30卷 150-157页

作者： xu Xie Ming Zhong tan Zhao Cong Wang Key Laboratory for Ecological Metallurgy of Multimetallic Mineral(Ministry of Education) Northeastern UniversityShenyang 110819LiaoningChina School of Metallurgy Northeastern UniversityShenyang 110819LiaoningChina State Key Laboratory of Advanced Special Steel Shanghai UniversityShanghai 200444China State Key Laboratory of Metal Material for Marine Equipment and Application Ansteel Co.Ltd.Anshan 114021LiaoningChina

Fused CaF_(2)-TiO_(2) fluxes have been designed,prepared,and applied in the flux cored wires to join EH36 shipbuilding steels under high heat input electro-gas welding.Ensuing microstructural evolution in the weld metals subjected to varied CaF_(2)-TiO_(2) flux cored wires has been fully documented.It has been demonstrated that as the content of TiO2 in the fused fluxes increases,columnar grain size increases,and major constituents in the weld metal change from lath bainite,to granular bainite,and then to acicular ferrite.Such phenomena are elucidated via salient chemical reactions involving oxygen pickup and concurrent titanium transfer.

关键词： Microstructural evolution Elemental variation Electro-gas welding High heat input Shipbuilding steel

Pilot time-varying control behavior modeling in refractory period with aircraft failures

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Science China(Technological Sciences) 2023年第7期66卷 2000-2012页

作者： xu ShuTing tan WenQian WANG WeiJun SUN LiGuo School of Aeronautic Science and Engineering Beihang UniversityBeijing 100191China Jiangxi Research Institute of Beihang University Nanchang 330000China

Modeling human pilot control behavior aims to understand and describe how humans control aircrafts and devices,to provide a foundation for the study of the dynamic characteristics of the human-vehicle system.In the presence of aircraft failures,the human pilot has a control process of the refractory period,which may cause adverse aircraft-pilot couplings,and even lead to loss-of-control events.This refractory period will make the pilot emerge with time-varying and adaptive features.This paper investigates how pilot control behavior changes to adapt to the aircraft failure situation and develops a time-varying pilot model during the refractory period.Six aviation pilots performed a human-in-the-loop simulation experiment on a ground flight simulator to simulate the failure situations for a pitch-tracking task.To characterize the pilot’s time-varying response mechanism,a time-frequency-spectrum method was used to analyze the pilot control signal.Main innovations in the proposed model can be embodied in the description of the fuzziness,time-varying,and adaptation of the pilot for the failures in the refractory period.Based on fuzzy logic theory,the pilot’s judgment and identification of failures are described.The adaptation of manual control behavior to time-varying aircraft dynamics is depicted by adaptive model theory.Time-domain and time-frequency-spectrum analysis show that the simulation results of the pilot model are consistent with the human-in-the-loop experimental results.The model simulation evaluations are within the range of the experimental evaluation,which shows the rationality of the timevarying behavior model of the human pilot in a failure refractory period.The model has practical values for guiding the pilot to deal with abnormal conditions and predicting nonlinear aircraft-pilot couplings.

关键词： time-varying system human pilot model fuzzy control simulation aircraft-pilot couplings

A collaborative assembly for low-voltage electrical apparatuses

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Frontiers of Information Technology & Electronic Engineering 2023年第6期24卷 890-905页

作者： Huanpei LYU Libin ZHANG Dapeng tan Fang xu College of Mechanical Engineering Zhejiang University of TechnologyHangzhou 310014China College of Digital Technology and Engineering Ningbo University of Finance and EconomicsNingbo 315175China

Low-voltage electrical apparatuses(LVEAs)have many workpieces and intricate geometric structures,and the assembly process is rigid and labor-intensive,and has little balance.The assembly process cannot readily adapt to changes in assembly situations.To address these issues,a collaborative assembly is proposed.Based on the requirements of collaborative assembly,a colored Petri net(CPN)model is proposed to analyze the performance of the interaction and self-government of robots in collaborative assembly.Also,an artificial potential field based planning algorithm(AFPA)is presented to realize the assembly planning and dynamic interaction of robots in the collaborative assembly of LVEAs.Then an adaptive quantum genetic algorithm(AQGA)is developed to optimize the assembly process.Lastly,taking a two-pole circuit-breaker controller with leakage protection(TPCLP)as an assembly instance,comparative results show that the collaborative assembly is cost-effective and flexible in LVEA assembly.The distribution of resources can also be optimized in the assembly.The assembly robots can interact dynamically with each other to accommodate changes that may occur in the LVEA assembly.

关键词： Low-voltage electrical apparatus Collaborative assembly Artificial potential field based planning Adaptive quantum genetic algorithm Dynamic interaction