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Mathematical foundation of turbulence generation-From symmetric to asymmetric Liutex

Journal of Hydrodynamics 2019年第3期31卷 632-636页

作者： Jian-ming Liu Yue Deng yi-sheng gao Sita Charkrit Chaoqun Liu School of Mathematics and Statistics Jiangsu Normal University Xuzhou 221116 China Department of Mathematics University of Texas at Arlington Arlington 76019 Texas USA Department of Physics University of Texas at Arlington Arlington 76019 Texas USA

Vortices have been regarded as the building blocks and muscles of turbulence for a long time. To better describe and analyze vortices or vortical structures, recently a new physical quantity called Liutex (previously named Rortex) is introduced to present the rigid rotation part of fluid motion (Liu et al. 2018). Since turbulence is closely related to the vortex, it can be postulated that there exists no turbulence without Liutex. According to direct numerical simulations (DNS) and experiments, forest of hairpin vortices has been found in transitional and low Reynolds number turbulent flows, while one-leg vortices are predominant in full developed turbulent flows. This paper demonstrates that the hairpin vortex is unstable. The hairpin vortex will be weakened or lose one leg by the shear and Liutex interaction, based on the Liutex definition and mathematical analysis without any physical assumptions. The asymmetry of the vortex is caused by the interaction of symmetric shear and symmetric Liutex since the smaller element of a pair of vorticity elements determines the rotational strength. For a 2-D fluid rotation, if a disturbance shear effects the larger element, the rotation strength will not be changed, but if the disturbance shear effects the smaller element, the rotation strength will be immediately changed due to the definition of the Liutex strength. For a rigid rotation, if the shearing part of the vorticity and Liutex present the same directions, e.g., clockwise, the Liutex strength will not be changed. If the shearing part of the vorticity and Liutex present different directions, e.g., one clockwise and another counterclockwise, the Liutex strength will be ***, the hairpin vortex could lose the symmetry and even deform to a one-leg vortex. The one-leg vortex cannot keep balance, and the chaotic motion and flow fluctuation are doomed. This is considered as the mathematical foundation of turbulence formation. The DNS results of boundary laye

关键词： Turbulence generation mathematical principle Liutex/Rortex asymmetry

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In vitro reconstitution guide for targeted synthetic metabolism of chemicals, nutraceuticals and drug precursors

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Synthetic and Systems Biotechnology 2016年第1期1卷 25-33页

作者： gao-yi Tan Faying Zhu Zixin Deng Tiangang Liu Key Laboratory of Combinatorial Biosynthesis and Drug Discovery(Wuhan University) Ministry of EducationAnd Wuhan University School of Pharmaceutical SciencesWuhan430071China Hubei Engineering Laboratory for Synthetic Microbiology Wuhan Institute of BiotechnologyWuhan430075China

With the developments in metabolic engineering and the emergence of synthetic biology,many breakthroughs in medicinal,biological and chemical products as well as biofuels have been achieved in recent *** an important barrier to traditional metabolic engineering,however,the identification of ratelimiting step(s)for the improvement of specific cellular functions is often ***,in the case of synthetic biology,more and more BioBricks could be constructed for targeted purposes,but the optimized assembly or engineering of these components for high-efficiency cell factories is still a *** to the lack of steady-state kinetic data for overall flux,balancing many multistep biosynthetic pathways is time-consuming and needs vast resources of labor and materials.A strategy called targeted engineering is proposed in an effort to solve this ***,a targeted biosynthetic pathway is to be reconstituted in vitro and then the contribution of cofactors,substrates and each enzyme will be analyzed *** is in vivo engineering or de novo pathway assembly with the guidance of information gained from in vitro *** demonstrate its practical application,biosynthesis pathways for the production of important products,***,nutraceuticals and drug precursors,have been engineered in Escherichia coli and Saccharomyces *** cases can be regarded as concept proofs indicating targeted engineering might help to create high-efficiency cell factories based upon constructed biological components.

关键词： Targeted engineering In vitro reconstitution Fatty acid Terpene Polyketide

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Impacts of the meteorological condition versus emissions reduction on the PM_(2.5) concentration over Beijing-Tianjin-Hebei during the COVID-19 lockdown

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Atmospheric and Oceanic Science Letters 2021年第4期14卷 38-44页

作者： Yanqing Zhang Zhaokun Ma yi gao Meigen Zhang State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijingChina Shandong Academy for Environmental Planning JinanChina

The impacts of the meteorological condition and emissions reduction on the aerosol concentration over the Beijing-Tianjin-Hebei(BTH) region during the COVID-19 lockdown were analyzed by conducting three numerical experiments,including one with the meteorological field in 2019 and MEIC-2019(2019 monthly Multi-resolution Emissions Inventory for China),one with the meteorological field in 2020 and MEIC-2019,and one with the meteorological field in 2020 and MEIC-2020,via a WRF-Chem *** numerical experiments were performed from 3 to 16 February in 2019 and in 2020,during which a severe fog-haze event(3-16 February 2020) occurred in the BTH region,with a simulated maximum daily PM2.5 of 245μg m-3 in Tangshan and 175μg m-3 in *** results indicate that the daily PM2.5 decreased by 5-150μg m-3 due to the emissions reduction and increased by 10-175 μg m-3 due to the meteorological condition in Beijing,Shijiazhuang,Cangzhou,Handan,Hengshui,Chengde,Zhangjiakou,and Tangshan from 7 to 14 *** the horizontal distribution,PM2.5 and different aerosol species concentrations from 7 to 14 February 2020 increased compared with those during the same period in 2019,indicating that the accumulation of pollutants caused by the unfavorable meteorological condition offset the decreases caused by the emissions reduction,leading to the high aerosol concentration during the COVID-19 lockdown.

关键词： PM_(2.5) WRF-Chem Meteorological condition Emissions reduction

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Use of Deep Learning for Continuous Prediction of Mortality for All Admissions in Intensive Care Units

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Tsinghua Science and Technology 2023年第4期28卷 639-648页

作者： Guangjian Zeng Jinhu Zhuang Haofan Huang Mu Tian yi gao Yong Liu Xiaxia Yu School of Biomedical Engineering Health Science CenterShenzhen UniversityShenzhen 518060China Shenzhen Hospital Southern Medical UniversityShenzhen 518060China

The mortality rate in the intensive care unit(ICU)is a key metric of hospital clinical *** enhance hospital performance,many methods have been proposed for the stratification of patients’different risk categories,such as severity scoring systems and machine learning ***,these methods make capturing time sequence information difficult,posing challenges to the continuous assessment of a patient’s severity during their hospital ***,we built a predictive model that can make predictions throughout the patient’s stay and obtain the patient’s risk of death in real *** proposed model performed much better than other machine learning methods,including logistic regression,random forest,and XGBoost,in a full set of performance evaluation ***,the proposed model can support physicians’decisions by allowing them to pay more attention to high-risk patients and anticipate potential complications to reduce ICU mortality.

关键词： deep learning representation learning mortality risk prediction critical care

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Novel insights into congenital surfactant dysfunction disorders by in silico analysis of ABCA3 proteins

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World Journal of Pediatrics 2023年第3期19卷 293-301页

作者： Guo-Liang Xiao Yuan gao Hu Hao Tao Wei Chun Hong Yue Wang ying-yi Lin Xiu-Fang Chi ying Liu Hong-yi gao Chuan Nie Department of Neonatology Guangdong Women and Children HospitalGuangzhou 511442China Guangdong Neonatal ICU Medical Quality Control Center Guangzhou 511442China Department of Marine Science College of OceanographySouth China Agricultural UniversityGuangzhouChina Department of Neonatology The Sixth Affiliated Hospital of Sun Yat-Sen UniversityGuangzhouChina Department of Bioengineering College of Food Science and Institute of Food BiotechnologySouth China Agricultural UniversityGuangzhouChina Research Center for Micro-Ecological Agent Engineering and Technology of Guangdong Province GuangzhouChina Department of Thoracic Surgery Guangdong Women and Children HospitalGuangzhouChina Department of Pathology Guangdong Women and Children HospitalGuangzhou 511442GuangzhouChina

Surfactants produced by typeⅡalveolar epithelial cells(AT2 cells)are usually present in inclusion organelles called lamellar bodies(LBs).The ATP-binding cassette subfamily A member 3(ABCA3)transporter primarily exists in AT2 cells and is generally considered to be one of the critical regulators of biogenesis of LBs and surfactant metabolism in the lungs[1-4].ABCA3 mutations are the most com-mon cause of congenital surfactant dysfunction disorders(CSDDs),resulting in fatal neonatal respiratory distress and pediatric or adult interstitial lung disease[3,5-7].More than 200 disease-associated ABCA3 variants have been identi-fied in symptomatic infants and children[8].The estimated prevalence of deleterious ABCA3 mutations in the popu-lation is 1/70-1/33,with a predicted disease incidence of 1/20,000-1/4400[7].

关键词： congenital metabolism distress

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Exploration of structure sensitivity of gold nanoparticles in low-temperature CO oxidation

INDUSTRIAL CHEMISTRY & MATERIALS

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INDUSTRIAL CHEMISTRY & MATERIALS 2024年第2期2卷 321-327页

作者： ying, Lei Han, Yu Zhu, Beien gao, yi Chinese Acad Sci Shanghai Inst Appl Phys Key Lab Interfacial Phys & Technol Shanghai 201800 Peoples R China Univ Chinese Acad Sci Beijing 100049 Peoples R China Chinese Acad Sci Shanghai Adv Res Inst Phonon Sci Res Ctr Carbon Dioxide Shanghai 201210 Peoples R China Chinese Acad Sci Shanghai Adv Res Inst Key Lab Low Carbon Convers Sci & Engn Shanghai 201210 Peoples R China

Gold nanoparticles (NPs) exhibit remarkable catalytic activity in low-temperature CO oxidation and their performance is highly dependent on size and shape. However, the underlying mechanism isn't fully understood yet. Herein, we combine density functional theory calculations, a multiscale structure reconstruction model, and kinetic Monte Carlo simulations to investigate the activity and structure sensitivity of Au NPs under different reaction conditions. The results indicate that increasing the partial pressure ratio of O2 to CO leads to the decrease of optimal reaction temperature accompanied with the increase of performance. At low temperatures, the morphology of the NPs evolves to expose a higher proportion of (110) facets to promote the activity significantly. Moreover, the size dependence analysis suggests that O2-rich conditions are favorable for small-sized NPs, while CO-rich conditions favor the large-sized NPs. These findings not only enrich our basic understanding of the structure-reactivity relationship and the origin of structure sensitivity in gold-catalysis, but provide a guide for rational design of Au ***: Kinetic Monte Carlo;CO oxidation;Gold catalysis;Nanoparticles.

关键词： Kinetic Monte Carlo CO oxidation Gold catalysis Nanoparticles

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Liutex theoretical system and six core elements of vortex identification

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Journal of Hydrodynamics 2020年第2期32卷 197-211页

作者： yi-qian Wang yi-sheng gao Hongyi Xu Xiang-rui Dong Jian-ming Liu Wen-qian Xu Meng-long Chen Chaoqun Liu School of Mathematical Science Soochow UniversitySuzhou215006China College of Aerospace Engineering Nanjing University of Aeronautics and AstronauticsNanjing210016China Aeronautics and Astronautics Department Fudan UniversityShanghai200433China School of Energy and Power Engineering University of Shanghai for Science and TechnologyShanghai200093China School of Mathematics and Statistics Jiangsu Normal UniversityXuzhou221116China Faculty of Mechanical Engineering and Automation Zhejiang Sci-Tech UniversityHangzhou310018China SimpleHPC LTD. Shanghai200030China Department of Mathematics University of Texas at ArlingtonArlington76019USA

The third-generation vortex identification method of Liutex(previously called Rortex)was introduced by the team led by *** Liu from University of Texas at Arlington to mathematically extract the rigid rotation part from the fluid motion,and thus to define and visualize *** the vorticity-based first generation and the scalar-valued second generation,Q,λ2,Δandλci methods for example,the Liutex vector provides a unique,mathematical and systematic way to define vortices and visualize vortical structures from multiple perspectives without *** this article,we summarize the recent developments of the Liutex framework and discuss the Liutex theoretical system including its existence,uniqueness,stability,Galilean invariance,locality and globality,decomposition in tensor and vector forms,Liutex similarity in turbulence,and multiple Liutex-based vortex visualization methods including Liutex lines,Liutex magnitude iso-surfaces,Liutex-Ωmethod,and Liutex core line method,etc..Thereafter,the six core elements of vortex identification,including(1)absolute strength,(2)relative strength,(3)local rotational axis,(4)vortex rotation axes,(5)vortex core size,(6)vortex boundary,are used as touchstones against which the Liutex vortex identification system is *** is demonstrated with illustrative examples that the Liutex system is able to give complete and precise information of all six core elements in contrast to the failure and inaccuracy of the first and second-generation *** important concept that vorticity cannot represent vortex and the superiority of the Liutex system over previous methods are reiterated and stated in appropriate places throughout the ***,the article concludes with future perspectives,especially the application of the Liutex system in studying turbulence mechanisms encouraged by the discovery of Liutex similarity *** a newly defined physical quantity,Liutex may open a door for quantified vortex and turbulenc

关键词： Vortex identification Liutex vector six core elements Liutex core line Liutex similarity turbulence

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Response Characteristics and Adiabatic Heating during High Strain Rate for TRIP Steel and DP Steel

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Journal of Iron and Steel Research International 2015年第1期22卷 48-54页

作者： yi gao Chao XU Zhong-ping HE Yan-lin HE Lin LI School of Materials Science and Engineering Shanghai University

By using a static and high-speed material testing machine, tensile deformation behaviors of two kinds of Si- Mn TRIP （transformation induced plasticity） steels and DP （dual phase） steel were studied in a large range of strain rates （0.001-2000 s 1）. Temperature variation during adiabatic heating and the amount of retained austenite at fracture were measured by an infrared thermometer and an Xray stress analyser, respectively. The microstructure of steels was observed by optical microscopy （OM） and scanning electron microscopy （SEM） before and after tensile test. It was found from the experimental results that the tensile strength of these steels increased, and the fracture elonga- tion firstly decreased and subsequently increased, as the strain rate increased in the range ＂of 0.1 - 2000 s -1. The temperature raised during adiabatic heating of TRIP steel was in the range of 100- 300℃, while that of the DP steel was in the range of 100-220℃ . The temperature rise of these steels increased with increasing the strain rate, as well as the amount of the transformed retained austenite in TRIP steels. It was confirmed that austenite to martensite transformation is not suppressed by adiabatic heating.

关键词： strain rate TRIP steel adiabatic heating retained austenite

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3D printing preview for stereo-lithography based on photopolymerization kinetic models

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Bioactive Materials 2020年第4期5卷 798-807页

作者： yi gao Lei Xu Yang Zhao Zhengwei You Qingbao Guan State Key Laboratory for Modification of Chemical Fibers and Polymer Materials Shanghai Belt and Road Joint Laboratory of Advanced Fiber and Low-dimension Materials(Donghua University)College of Materials Science and EngineeringDonghua UniversityShanghai201620PR China Center for Combustion Energy and Key Laboratory for Thermal Science and Power Engineering of MOE Tsinghua UniversityBeijing100084China Institute of Agricultural Facilities and Equipment Jiangsu Academy of Agricultural SciencesKey Laboratory for Protected Agricultural Engineering in the Middle and Lower Reaches of Yangtze RiverMinistry of Agriculture and Rural AffairsNanjing210014PR China

The diversity of biomedical applications makes stereolithographic(SL)three-dimensional(3D)printing process complex.A strategy was developed to simulate the layer-by-layer fabrication of 3D printed products combining polymerization kinetic with reaction conditions to realize print *** a representative example,the typical UV-curable dental materials based on epoxy acrylate and photoinitiator with different molar ratios was exposed under varying intensity of UV light to verify the simulation results.A theoretical kinetics model containing oxygen inhibition was ***-situ FTIR was employed to measure propagation and termination constants while coupled UV/vis was performed to examine the law of light attenuation during cure reaction,even with various colours and *** results showed that the correlation coefficient square between the experiments and simulations of epoxy acrylate with 1%,2%and 3%initiator upon 20 mW/cm2 UV light are 0.8959,0.9324 and 0.9337,***,our simulation of photopolymerization for SL 3D printing successfully realized visualization of printing quality before practically printing the targeted biomedical objects with complex topology structures.

关键词： 3D printing preview Photopolymerization kinetics Biomedical applications Dental materials Epoxy acrylate

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Decadal expansion and contraction of permafrost in the Three-River Source Region,Qinghaie-Tibet Plateau(1901-2020)

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Advances in Climate Change Research 2023年第2期14卷 226-236页

作者： Fang-Fang CHEN Dong-Liang LUO yi-Ting gao Wen-Jie LEI State Key Laboratory of Frozen Soil Engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China University of Chinese Academy of Sciences Beijing 100049China

Permafrost and its spatiotemporal variation considerably influence the surface and sub-surface hydrological processes,biogeochemical cycles,fauna and flora growth and cold region engineering projects in the Three-River Source Region(TRSR),Qinghai–Tibet ***,the dynamics of permafrost over a relatively long term duration(e.g.>100 years)in the TRSR is not well ***,the spatial and temporal variations of the temperature at the top of the perennially frozen/unfrozen ground(TTOP),active layer thickness(ALT)in permafrost regions and the maximum depth of frost penetration(MDFP)in the seasonally frozen ground of the TRSR during 1901–2020 were simulated using the TTOP model and Stefan equation driven by the widely used reanalysis Climatic Research Unit 4.05 *** revealed that the permafrost in the TRSR over the past 120 years did not degrade monotonically but experienced considerable fluctuations in area with the decadal oscillations of climate warming and cooling:shrinking from 263.9×10^(3)km^(2)in the 1900s to 233.3×10^(3)km^(2)in the 1930s,expanding from 232.3×10^(3)km^(2)in the 1940s to 260.9×10^(3)km^(2)in the 1970s and shrinking again from 254.1×10^(3)km^(2)in the 1980s to 228.9×10^(3)km^(2)in the *** regional average TTOP increased from−1.34±2.74℃in the 1910s to−0.48±2.69℃in the 2010s,demonstrating the most noticeable change for the extremely stable permafrost(TTOP3.0 m by 12%from 1901 to ***,minor changes were observed for the regional average MDFP,probably due to the increase in the area proportion of MDFP3.5 m(owing to the transformation of permafrost to seasonally frozen ground)by 7.39%and 4.77%,*** findings can facilitate an in-depth understanding of permafrost dynamics and thus provide a scientific reference for eco-environment protection and s

关键词： Three-River Source Region Permafrost TTOP model Stefan equation Qinghaie-Tibet Plateau

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