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Coalescence-dominated microstructure evolution during solidification of 20SiMn steel

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Journal of Iron and Steel Research International 2020年第5期27卷 506-516页

作者： Xiao-ping ma Dian-zhong Li Shenyang National Laboratory for materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016LiaoningChina

The evolution of microstructures during the solidification of 20SiMn steel was *** dominant role of coalescence was revealed by analyzing the quenched microstructures and the solute *** the parameter range investigated,including the slow solidification,the fast solidification and the directional solidification,the coalescence can happen at multiple solidification stages and on *** the directional solidification,the ternary and fourth dendritic arms coalesce into the secondary dendritic arms,and the secondary dendritic arms further coalesce to produce the cellular *** cellular crystals become coarse through further *** the non-directional solidification,the initial microstructures are discrete crystals without the dendritic *** the dendritic arms and dendritic stems appearing in the later solidification stage are produced by the coalescence on *** coalescence is more significant in the later solidification *** mechanism of coalescence is attributed to different melt compositions in different local domains and the reduction of the interface energy.

关键词： Solidification Microstructure Coalescence Steel Microsegregation

An adaptive sequential experiment design method for model validation

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Chinese Journal of Aeronautics 2020年第6期33卷 1661-1672页

作者： Ke FANG Yuchen ZHOU ping ma Control and Simulation Center Harbin Institute of TechnologyHarbin 150080China

Efficient experiment design is of great significance for the validation of simulation model with high nonlinearity and large input *** validation experiment raises the cost while insufficient test increases the risks of accepting an invalid *** this paper,an adaptive sequential experiment design method combining global exploration criterion and local exploitation criterion is *** exploration criterion utilizes discrepancy metric to improve the space-filling property of the design points while the exploitation criterion employs the leave one out error to discover informative *** avoid the clustering of samples in the local region,an adaptive weight updating approach is provided to maintain the balance between exploration and ***,the credibility distribution function characterizing the relationship between the input and result credibility is introduced to support the model validation experiment ***,six benchmark problems and an engineering case are applied to examine the performance of the proposed *** experiments indicate that the proposed method achieves satisfactory performance for function approximation in accuracy and convergence.

关键词： Adaptive sequential experiment design Credibility distribution function Gaussian process model Metamodeling Model validation

The Applied Research of Fracture in Three-point Bending to Blanking of Bearing Steel

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上海交通大学学报 2004年第Z2期38卷 199-205页

作者： Youtang Li ping ma Changfeng Yan College of Mechano-Electronic Engineering Lanzhou University of Technology Lanzhou730050 China College of Mechano-Electronic Engineering Lanzhou University of Technology Lanzhou730050 China College of Mechano-Electronic Engineering Lanzhou University of Technology Lanzhou730050 China

The application of fracture in three-point bending to blanking of bearing steel is studied in this paper. Several mechanical models of stress blanking are discussed at first. And then the experiments have been made in special equipment of three-point bending designed by us. Several problems, such as the suitable span, the relations between bending and tension bending complex, the ratio of blanking length to the diameter, the relations of blank length to force, the feature of fracture, are studied through the experiments. The suitable parameters of three-point bending to blanking, depth and tip radius of notch and the ratio between blanking length and stick diameter have been proposed.

关键词： bearing steel three points bending blanking crack technique fracture design

Activity of Stress-related Antioxidative Enzymes in the Invasive Plant Crofton Weed(Eupatorium adenophorum)

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Journal of Integrative Plant Biology 2007年第11期49卷 1555-1564页

作者： ping Lu Wei-Guo Sang Ke-ping ma Key Laboratory of Vegetation Ecology and Environment Change Institute of Botany the Chinese Academy of Sciences Beijing 100093 China Resources and Environmental Sciences College Northeast Agrfcultural University Harbin 150030 China

Crofton weed is an invasive weed in southwestern China. The activities of several antioxidative enzymes involved in plant protection against oxidative stress were assayed to determine physiological aspects of the crofton weed that might render the plant vulnerable to environmental stress. Stresses imposed on crofton weed were heat （progressively increasing temperatures： 25 ℃, 30 ℃, 35 ℃, 38℃ and 42 ℃ at 24 h intervals）, cold （progressively decreasing temperatures： 25 ℃, 20 ℃, 15℃, 10 ℃ and 5℃ at 24h intervals）, and drought （without watering up to 4days）. The three stresses induced oxidative damage as evidenced by an increase in lipid peroxidation. The effect varied with the stress imposed and the length of exposure. The activity of superoxide dismutase （SOD） increased in response to all stresses but was not significantly different from the controls （P 〈 0.05） when exposed to cold stress. Catalase （CAT） activity decreased in response to heat and drought stress but increased when exposed to cold conditions. Guaiacol peroxidase （POD） and glutathione reductase （GR） activities increased in response to cold and drought but decreased in response to heat stress. The activity of ascorbata peroxidase （APX） responded differently to all three stresses. Monodehydroascorbate reductase （MDHAR） activity decreased in response to heat and drought, and slightly increased in response to the cold stress but was not significantly different from the controls （P 〈 0.05）. The activity of dehydroascorbata reductase （DHAR） increased in response to all three stresses. Taken together, the co-ordinate increase of the oxygen-detoxifying enzymes might be more effective to protect crofton weed from the accumulation of oxygen radicals at low temperatures rather than at high temperatures.

关键词： antioxidative enzymes crofton weed invasive plant stress.

Differential Responses of the Activities of Antioxidant Enzymes to Thermal Stresses between Two Invasive Eupatorium Species in China

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Journal of Integrative Plant Biology 2008年第4期50卷 393-401页

作者： ping Lu Wei-Guo Sang Ke-ping ma Key Laboratory of Vegetation and Environment Change Institute of Botany the Chinese Academy of Sciences Beijing 100093 China Resources and Environmental Sciences College Northeast Agricuitural University Harbin 150030 China

The effect of thermal stress on the antioxidant system was investigated in two invasive plants, Eupatorium adenophorum Spreng. and E. odoratum L. The former is sensitive to high temperature, whereas the latter is sensitive to low temperature. Our aim was to explore the relationship between the response of antioxidant enzymes and temperature in the two invasive weeds with different distribution patterns in China. Plants were transferred from glasshouse to growth chambers at a constant 25 ℃for I week to acclimatize to the environment. For the heat treatments, temperature was increased stepwise to 30, 35, 38 and finally to 42 ℃. For the cold treatments, temperature was decreased stepwise to 20, 15, 10 and finally to 5 ℃. Plants were kept in the growth chambers for 24 h at each temperature step. In E. adenophorum, the coordinated increase of the activities of antioxidant enzymes was effective in protecting the plant from the accumulation of active oxygen species （AOS） at low temperature, but the activities of catalase （CAT）, guaiacol peroxidase （POD）, ascorbate peroxidase （APX）, glutathione reductase （GR）, and monodehydroascorbate reductase （MDAR） were not accompanied by the increase of superoxide dismutase （SOD） during the heat treatments. As a result, the level of lipid peroxidation in E. adenophorum was higher under heat stress than under cold stress. In E. odoratum, however, the lesser degree of membrane damage, as indicated by low monodehydroascorbate content, and the coordinated increase of the oxygen. Datoxifying enzymes were observed in heat-treated plants, but the antioxidant enzymes were unable to operate in cold stress. This indicates that the plants have a higher capacity for scavenging oxygen radicals in heat stress than in cold stress. The different responses of antioxidant enzymes may be one of the possible mechanisms of the differences in temperature sensitivities of the two plant species.

关键词： antioxidant enzyme system cold stress Eupatorium adenophorum Eupatorium odoratum heat stress invasive plants.

Nanoplatform-based cellular reactive oxygen species regulation for enhanced oncotherapy and tumor resistance alleviation

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Chinese Chemical Letters 2023年第9期34卷 85-99页

作者： Meifang Wang ping’an ma Jun Lin State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China

The cancer cells realize their proliferation and metastasis activities based on the special redox adaptation to increased reactive oxygen species(ROS)level,which inversely makes them sensitive to external interference with their redox *** view of this,in recent decades,researchers have made great efforts to construct a series of novel nanoplatform-based ROS-mediated cancer therapies through increasing ROS generation and inhibiting the ROS ***,the multidrug resistance and thermoresistance of tumor are closely related to tumor redox ***,numerous works have shown that ROS regulation in cancer cells can intervene in the expression,function and stability of related proteins to achieve reversal of tumor *** this review,the recent researches about ROS-regulating nanoagents on cancer therapy and tumor resistance alleviation have been well ***,the challenges and research directions of ROS-regulating nanoagents for future clinical translation are also discussed.

关键词： Nanoagents ROS regulation ROS-mediated cancer therapy Multidrug resistance Thermoresistance

Effects of progressive drought on photosynthesis and partitioning of absorbed light in apple trees

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Journal of Integrative Agriculture 2015年第4期14卷 681-690页

作者： ma ping BAI Tuan-hui ma Feng-wang College of Horticulture Northwest A&F University/State Key Laboratory of Crop Stress Biology for Arid Areas

To understand how drought stress affects CO2 assimilation and energy partitioning in apple（malus domestica Borkh.）, we investigated photosynthesis and photo-protective mechanisms when irrigation was withheld from potted Fuji trees. As the drought progressing, soil relative water content（SRWC） decreased from 87 to 24% in 15 d; this combined the decreasing in leaf relative water content（LRWC）, net photosynthesis rate（P n） and stomatal conductance（G s）. However, the concentrations of chlorophylls（Chl） remained unchanged while P n values were declining. Photochemistry reactions were slightly down-regulated only under severe drought. Rubisco activity was significantly decreased as drought conditions became more severe. The actual efficiency of photosystem II（ΦPSII） was diminished as drought became more intense. Consequently, xanthophyll-regulated dissipation of thermal energy was greatly enhanced. Simultaneously, the ratio of ΦPSII to the quantum yield of carbon metabolism, which is measured under non-photorespiratory conditions, increased in parallel with drought severity. Our results indicate that, under progressive drought stress, the reduction in photosynthesis in apple leaves can be attributed primarily to stomatal limitations and the inhibited capacity for CO2 fixation. Xanthophyll cycle-dependent thermal dissipation and the Mehler reaction are the most important pathways for dispersing excess energy from apple leaves during periods of drought stress.

关键词： apple drought stress energy dissipation photosynthesis

Simulation study on cooperation behaviors and crowd dynamics in pedestrian evacuation

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Chinese Physics B 2020年第3期29卷 488-495页

作者： Ya-ping ma Hui Zhang China Research Center for Emergency management Wuhan University of TechnologyWuhan 430070China School of Safety Science and Emergency management Wuhan University of TechnologyWuhan 430070China Institute of Public Safety Research Department of Engineering PhysicsTsinghua UniversityBeijing 100084China

Pedestrian evacuation is actually a process of behavioral evolution. Interaction behaviors between pedestrians affect not only the evolution of their cooperation strategy, but also their evacuation paths-scheduling and dynamics features. The existence of interaction behaviors and cooperation evolution is therefore critical for pedestrian evacuation. To address this issue, an extended cellular automaton(CA) evacuation model considering the effects of interaction behaviors and cooperation evolution is proposed here. The influence mechanism of the environment factor and interaction behaviors between neighbors on the decision-making of one pedestrian to path scheduling is focused. Average payoffs interacting with neighbors are used to represent the competitive ability of one pedestrian, aiming to solve the conflicts when more than one pedestrian competes for the same position based on a new method. Influences of interaction behaviors, the panic degree and the conflict cost on the evacuation dynamics and cooperation evolution of pedestrians are discussed. Simulation results of the room evacuation show that the interaction behaviors between pedestrians to a certain extent are beneficial to the evacuation efficiency and the formation of cooperation behaviors as well. The increase of conflict cost prolongs the evacuation time. Panic emotions of pedestrians are bad for cooperation behaviors of the crowd and have complex effects on evacuation time. A new self-organization effect is also presented.

关键词： pedestrian evacuation evacuation time interaction behaviors cooperation

Target localization method of non-cooperative spacecraft on on-orbit service

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Chinese Journal of Aeronautics 2022年第11期35卷 336-348页

作者： Yingxiao LI Ju HUO ping ma Ruiye JIANG Control and Simulation Center Harbin Institute of TechnologyHarbin 150001 China

With the explosion of the number of meteoroid/orbital debris in terrestrial space in recent years, the detection environment of spacecraft becomes more complex. This phenomenon causes most current detection methods based on machine learning intractable to break through the two difficulties of solving scale transformation problem of the targets in image and accelerating detection rate of high-resolution images. To overcome the two challenges, we propose a novel noncooperative target detection method using the framework of deep convolutional neural ***, a specific spacecraft simulation dataset using over one thousand images to train and test our detection model is built. The deep separable convolution structure is applied and combined with the residual network module to improve the network’s backbone. To count the different shapes of the spacecrafts in the dataset, a particular prior-box generation method based on K-means cluster algorithm is designed for each detection head with different scales. Finally, a comprehensive loss function is presented considering category confidence, box parameters, as well as box confidence. The experimental results verify that the proposed method has strong robustness against varying degrees of luminance change, and can suppress the interference caused by Gaussian noise and background complexity. The mean accuracy precision of our proposed method reaches 93.28%, and the global loss value is 13.252. The comparative experiment results show that under the same epoch and batchsize, the speed of our method is compressed by about 20% in comparison of YOLOv3, the detection accuracy is increased by about 12%, and the size of the model is reduced by nearly 50%.

关键词： Spacecraft service High resolution image Object detection Complex environment Lightweight model