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Dynamics of a discrete predator-prey model with Holling-II functional response

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International Journal of Biomathematics 2021年第8期14卷 253-272页

作者： Yuqing Liu Xianyi Li Department of Big Data Science School of ScienceZhejiang University of Science and TechnologyHangzhou 310023P.R.China

In this paper,we use a semidiscretization method to derive a discrete predator–prey model with Holling type II,whose continuous version is stated in[F.Wu and Y.J.Jiao,Stability and Hopf bifurcation of a predator-prey model,Bound.Value Probl.129(2019)1–11].First,the existence and local stability of fixed points of the system are investigated by employing a key lemma.Then we obtain the sufficient conditions for the occurrence of the transcritical bifurcation and Neimark–Sacker bifurcation and the stability of the closed orbits bifurcated by using the Center Manifold theorem and bifurcation theory.Finally,we present numerical simulations to verify corresponding theoretical results and reveal some new dynamics.

关键词： Discrete predator-prey system semidiscretization method transcritical bifurcation Neimark-Sacker bifurcation

Tracking the historical urban development by classifying Landsat MSS data with training samples migrated across time and space

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International Journal of Digital Earth 2023年第1期16卷 2487-2502页

作者： Zemin Feng Yuqing Liu Yan Shi Jun Yang Department of Earth System Science Institute for Global Change StudiesMinistry of Education Ecological Field Station for East Asian Migratory BirdsTsinghua UniversityBeijingPeople’s Republic of China Anhui Urban&Rural Planning and Design Institute Co. Ltd.HefeiPeople’s Republic of China Beijing Hanbolin Institute of Surveying and Mapping BeijingPeople’s Republic of China

To reveal the historical urban development in large areas using satellite data such as Landsat MSS still need to overcome many challenges.One of them is the need for high-quality training samples.This study tested the feasibility of migrating training samples collected from Landsat MSS data across time and space.We migrated training samples collected for Washington,D.C.in 1979 to classify the city’s land covers in 1982 and 1984.The classifier trained with Washington,D.C.’s samples were used in classifying Boston’s and Tokyo’s land covers.The results showed that the overall accuracies achieved using migrated samples in 1982(66.67%)and 1984(65.67%)for Washington,D.C.were comparable to that of 1979(68.67%)using a random forest classifier.Migration of training samples between cities in the same urban ecoregion,i.e.Washington,D.C.,and Boston,achieved higher overall accuracy(59.33%)than cities in the different ecoregions(Tokyo,50.33%).We concluded that migrating training samples across time and space in the same urban ecoregion are feasible.Ourfindings can contribute to using Landsat MSS data to reveal the historical urbanization pattern on a global scale.

关键词： Land cover classifier training samples Landsat MSS KH-9

Automated Segmentation of the Brainstem,Cranial Nerves and Vessels for Trigeminal Neuralgia and Hemifacial Spasm

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Journal of Beijing Institute of Technology 2023年第5期32卷 631-639页

作者： yuqing Yang Zhiwen liu School of Intergrated Circuits and Electronics Beijing Institute of TechnologyBeijing 100081China

Accurate localization of cranial nerves and responsible blood vessels is important for diagnosing trigeminal neuralgia(TN)and hemifacial spasm(HFS).Manual delineation of the nerves and vessels on medical images is time-consuming and labor-intensive.Due to the development of convolutional neural networks(CNNs),the performance of medical image segmentation has been improved.In this work,we investigate the plans for automated segmentation of cranial nerves and responsible vessels for TN and HFS,which has not been comprehensively studied before.Different inputs are given to the CNN to find the best training configuration of segmenting trigeminal nerves,facial nerves,responsible vessels and brainstem,including the image modality and the number of segmentation targets.According to multiple experiments with seven training plans,we suggest training with the combination of three-dimensional fast imaging employing steady-state acquisition(3D-FIESTA)and three-dimensional time-of-flight magnetic resonance angiography(3DTOF-MRA),and separate segmentation of cranial nerves and vessels.

关键词： trigeminal nerves facial nerves responsible vessels medical image segmentation

Improved Dynamics Model of Locomotive Traction Motor with Elasticity of Rotor Shaft and Supporting Bearings

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Chinese Journal of Mechanical Engineering 2022年第5期35卷 333-350页

作者： Yuqing Liu Zaigang Chen Jieyu Ning Kaiyun Wang Wanming Zhai State Key Laboratory of Traction Power Southwest Jiaotong UniversityChengdu 610031China

The locomotive traction motor is described as a rotor-bearing system coupling the kinetic equations of the traction shaft and its support bearings with the determination of their elastic deformations in this study.Under the effect of excitations induced by the dynamic rotor eccentric distance and time-varying mesh stiffness,the elastic structure deformations of the shaft and support bearings are formulated in the vibration environment of the locomotive.In addition,the nonlinear contact forces between the components of the rolling bearing,the lubricating oil film,and radial clearance are comprehensively considered in this study.The results indicate that the elastic deformations of the shaft and bearings can change the dynamic responses of the traction motor and its support bearings.There are large differences between the ranges of the rotor motion calculated by the rigid and the flexible traction motor models when the intensified wheel-rail interaction is considered.With the increase of the rotor eccentricity,the results underscore the role of the elasticity of traction shaft and support bearings in dynamic researches of the traction motor.The critical value of the initial eccentric distance for the rub-impact phenomenon decreases from 1.23 mm to 1.15 mm considering the flexible effect of the shaft and bearings.This dynamics model of the traction motor can provide more accurate and reasonable simulation results for correlational dynamic researches.

关键词： Traction motor Bearing Gear mesh Vehicle-track coupled dynamics

Strain boosts CO oxidation on Ni single-atom-catalyst supported by defective graphene

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Chinese Chemical Letters 2023年第2期34卷 295-300页

作者： Quanguo Jiang Yushuai Qian Yuqing Liu Min Huang Zhimin Ao College of Mechanics and Materials Hohai UniversityNanjing 210098China Guangzhou Key Laboratory Environmental Catalysis and Pollution Control Guangdong Key Laboratory of Environmental Catalysis and Health Risk ControlInstitute of Environmental Health and Pollution ControlSchool of Environmental Science and EngineeringGuangdong University of TechnologyGuangzhou 510006China

In order to realize the sulfur and water resistance and facilitate the CO oxidation reactions,the effects of strain on the adsorption of CO,O_(2),SO_(2)and H_(2)O molecules on Ni single-atom-catalyst supported by single-carbon-vacancy graphene(Ni-SG) have been studied based on first principles calculations.It shows that the compressive strain increases the adsorption energies of all above mentioned molecules on Ni-SG,where SO_(2)is adsorbed more strongly on Ni-SG than CO.However,in the presence of tensile strain,the adsorption energies decreases significantly when the molecules(O_(2)and SO_(2)) obtain electrons from NiSG,while the adsorption energies just slightly decrease when the molecules(CO and H_(2)O) lose electrons to Ni-SG,which finally achieves the preferential adsorption of CO and O_(2)molecules on Ni-SG by tensile strain.In addition,with tensile strain increasing to 10%,the rate-limited energy barrier along Eley-Rideal(ER) path monotonically increases from 0.77 eV to 0.98 eV,while the rate-limited energy barrier along Langmuir-Hinshelwood(LH) path monotonically decreases from 0.54 eV to 0.44 eV,indicating that the tensile strain can facilitate the LH mechanism while imped the ER mechanism on Ni-SG.The Hirshfeld charge and orbital levels of O_(2)and CO molecules are modulated by the tensile strain,which plays an important role for the decreasing of energy barriers for CO oxidation.Overall,the tensile strain can enhance the sulfur and water resistance of Ni-SG,as well as boost the CO oxidation reactions.

关键词： Strain effect Ni single-atom-catalyst Preferential adsorption CO oxidation First principles calculations

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基于DBSE-Net的大田稻穗图像分割

农业工程学报 2022年第13期38卷 202-209页

作者：宋余庆杨东川徐立章刘哲江苏大学计算机科学与通信工程学院镇江212013 江苏大学农业工程学院镇江212013

稻穗精准分割是准确估测水稻产量的关键。为实现大田环境下不同品种与生育期稻穗的准确分割,该研究提出了基于注意力机制的稻穗分割网络(Double Branch Squeeze-and-Excitation Network,DBSE-Net)。首先,提出一个双分支压缩与激励(Doubl... 详细信息

稻穗精准分割是准确估测水稻产量的关键。为实现大田环境下不同品种与生育期稻穗的准确分割,该研究提出了基于注意力机制的稻穗分割网络(Double Branch Squeeze-and-Excitation Network,DBSE-Net)。首先,提出一个双分支压缩与激励(DoubleBranchSqueeze-and-Excitation,DBSE)注意力模块,通过同时使用全局平均池化(GlobalAverage Pooling,GAP)和全局最大池化(Global Max Pooling,GMP)编码输入特征的通道信息,以实现更精准的通道注意力推断。然后,为了强化稻穗特征并抑制背景区域特征,将DBSE模块添加到编码-解码分割框架中构建DBSE-Net分割网络。最后,在自采集的稻穗图像数据集上进行分割性能测试,DBSE-Net对稻穗分割的像素准确率、平均交并比和F1分数分别达到了94.32%、87.59%和91.86%,比次优模型DeepLabv3+的结果分别高出1.61、2.56和1.20个百分点,在单张256×256(像素)图像上耗时0.03s,是DeepLabv3+分割速度的5.3倍。在公开的稻穗图像数据集上进行泛化性能测试,DBSE-Net能够有效分割出稻穗区域。该研究结果表明,DBSE-Net能够对不同品种与生育期稻穗实现高效精准分割,具有良好的泛化性,可以为水稻产量评估提供参考。

关键词：模型图像分割卷积神经网络稻穗编码-解码结构注意力机制

Molecular pathology and clinical implications of diffuse glioma

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Chinese Medical Journal 2022年第24期135卷 2914-2925页

作者： Ruichao Chai Shengyu Fang Bo Pang Yuqing Liu Yongzhi Wang Wei Zhang Tao Jiang Department of Molecular Neuropathology Beijing Neurosurgical InstituteCapital Medical UniversityBeijing 100070China Department of Neurosurgery Beijing Tiantan HospitalCapital Medical UniversityBeijing 100070China Research Unit of Accurate Diagnosis Treatmentand Translational Medicine of Brain TumorsChinese Academy of Medical SciencesBeijing 100070China

The prognosis for diffusely infiltrating gliomas at World Health Organization(WHO)grade 2-4 remains dismal due to their heterogeneity.The rapid development of genome-wide molecular-profiling-associated studies has greatly promoted the accuracy of glioma classification.Thus,the latest version of the WHO classification of the central nervous system tumors published in 2021 has incorporated more molecular biomarkers together with histological features for the diagnosis of gliomas.Advanced usage of molecular pathology in clinical diagnostic practice provides also new opportunities for the therapy of patients with glioma,including surgery,radiotherapy and chemotherapy,targeted therapy,immunotherapy,and more precision clinical trials.Herein,we highlight the updates in the classification of gliomas according to the latest WHO guidelines and summarize the clinically relevant molecular markers by focusing on their applications in clinical practice.We also review the advances in molecular features of gliomas,which can facilitate the development of glioma therapies,thereby discussing the challenges and future directions of molecular pathology toward precision medicine for patients with glioma.

关键词： Glioma Molecular pathology tumor classification O^(6)-methylguanine-DNA methyltransferase Therapy

Surface wear evolution of traction motor bearings in vibration environment of a locomotive during operation

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Science China(Technological Sciences) 2022年第4期65卷 920-931页

作者： liu yuqing CHEN ZaiGang WANG KaiYun ZHAI WanMing State Key Laboratory of Traction Power Southwest Jiaotong UniversityChengdu 610031China

Wear is a major cause of bearing failure,however,compared with other impact failures,smooth wear is often neglected because of its slow gradualness.In a locomotive,under the effect of the intensified wheel-rail interaction and gear mesh,the surface wear can increase the radial clearances of motor bearings,trigger abnormal vibration and noise,and adversely affect the efficiency and safety of the traction motor.In this study,considering the mechanical structure of the traction motor,a locomotive-track spatially coupled dynamics model with traction power transmissions(LTMM)is adopted to provide accurate dynamic loads and obtain the dynamic responses of the system.From the perspective of contact stress and relative skidding at the roller-race interface,the causes and evolution of motor bearings surface wear are analyzed.The results indicate that the wear of inner races of motor bearings is uniform.The outer races of the driving/non-driving end bearings(DB or NDB)are worn in the loaded/main loadbearing regions.The increasing surface wear can increase the internal dynamic forces(e.g.,the centrifugal force of rotor and unbalanced magnetic pull)induced by the instantaneous eccentricity of the rotor,intensify the interactions between the roller and races,and deteriorate the vibrations of the traction motor and its neighboring components in the locomotive.In addition,the effects of the friction coefficient at the roller-race interface and track random irregularity are analyzed.This study offers a theoretical basis in service life prediction and design of the motor bearings.

关键词： wear rolling bearing traction motor railway vehicle dynamics

The Cotton GhWRKY91 Gene Negatively Regulates Root Elongation in Overexpressed Transgenic Arabidopsis thaliana

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Phyton-International Journal of Experimental Botany 2023年第11期92卷 2937-2946页

作者： Yueying liu yuqing Wang Lijiao Gu College of Forestry Hebei Agricultural UniversityBaoding071000China

WRKY transcription factors play important roles in plant growth,development,and stress responses.Our previous research has shown that the GhWRKY91 gene can delay age-,abscisic acid(ABA)-,and drought-induced leaf senescence when overexpressed in transgenic Arabidopsis plants.To explore in more depth the biological functions of the GhWRKY91 gene,we further observed the root growth of overexpressing transgenic Arabidopsis thaliana under ABA and drought treatment.In this study,we transplanted the germinated seeds of wild-type(WT)and three transgenic lines(OE-12,OE-13 and OE-20)to 1/2 MS solid medium containing ABA and different concentrations of mannitol(simulated drought treatment)for culturing.The results showed that the transgenic plants had dark green leaves and short root lengths when no stress treatment was added.After ABA and mannitol treatment,the root growth of the WT and transgenic Arabidopsis was inhibited to varying degrees,and the root length downregulation of the transgenic plants was higher than that of the WT,indicating that they were more sensitive to ABA and drought.A bimolecular fluorescence complementation(BiFC)assay showed that the GhWRKY91 and GhWRKY3 proteins interact and emit yellow fluorescence in tobacco leaf cells.These results indicate that the GhWRKY91 gene negatively regulates root elongation in transgenic Arabidopsis and provide a basis for further research on the molecular mechanism of its involvement in regulating cotton root development.

关键词： Cotton GhWRKY91 gene root elongation stress treatment BiFC