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Bifurcations of Limit Cycles in a Z_4-Equivariant Quintic Planar Vector Field

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Acta Mathematica Sinica,English Series 2010年第4期26卷 779-798页

作者： yu Hai WU Xue Di WANG Li xin tian Department of Mathematics Jiangsu University Zhenjiang 212013 P. R. China

In this paper, a Z4-equivariant quintic planar vector field is studied. The Hopf bifurcation method and polycycle bifurcation method are combined to study the limit cycles bifurcated from the compounded cycle with 4 hyperbolic saddle points. It is found that this special quintic planar polynomial system has at least four large limit cycles which surround all singular points. By applying the double homoclinic loops bifurcation method and Hopf bifurcation method, we conclude that 28 limit cycles with two different configurations exist in this special planar polynomial system. The results acquired in this paper are useful for studying the weakened 16th Hilbert＇s Problem.

关键词： compounded cycle double homoclinic loops stability bifurcation limit cycles distribution of limit cycles

高光谱预处理方法与多模型在分类判别中的对比研究

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光谱学与光谱分析 2025年第1期45卷 125-132页

作者：居雷于洁吴炎淼李丽卢天丁亚萍束茹欣上海烟草集团有限责任公司技术中心上海200082 上海大学化学系上海200444 上海数之微信息科技有限公司上海200444

高光谱技术能够快速、无损地获取丰富的信息,在植物研究和监测中已成为一种广泛应用的工具。茄科植物作为一种重要的经济农作物,与高光谱技术结合进行研究具有巨大的应用潜力。本研究采用高光谱技术对茄科植物的初烤后不同部位叶片进行... 详细信息

高光谱技术能够快速、无损地获取丰富的信息,在植物研究和监测中已成为一种广泛应用的工具。茄科植物作为一种重要的经济农作物,与高光谱技术结合进行研究具有巨大的应用潜力。本研究采用高光谱技术对茄科植物的初烤后不同部位叶片进行分类研究。采用Field Spec 3光谱辐射仪对293份不同部位的茄科植物粉末样本进行高光谱采样,采用S-G平滑以及一阶导数和二阶导数的方法对数据进行预处理,用于信息增强和去除噪声,并通过偏最小二乘法对数据进行降维,以减少冗余特征。基于降维数据,采样支持向量机、逻辑回归、K近邻、决策树、随机森林和梯度提升决策树这六种机器学习算法建立分类模型。结果显示,在分类任务中,经过一阶导数处理后,支持向量机模型最佳,在训练集和测试集上分别实现了100.0%和84.7%的准确率。经网格参数优化后确定最优参数为:最大深度不限制,最小样本分割数为4,估计器数量为200。参数优化后五折交叉验证准确率为88.1%,训练集准确率为100%,测试集准确率为86.4%。研究结果表明,预处理方法结合降维方法能够增强数据信息使得分类模型能够更好地捕捉茄科植物样本的特征。该研究对于快速、准确、无损地区分茄科植物的部位具有重要意义。

关键词：高光谱部位分类机器学习

Improved Plasmonic Hot‑Electron Capture in Au Nanoparticle/Polymeric Carbon Nitride by Pt Single Atoms for Broad‑Spectrum Photocatalytic H_(2)Evolution

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Nano-Micro Letters 2023年第8期15卷 423-435页

作者： Manyi Gao Fenyang tian xin Zhang Zhaoyu Chen Weiwei Yang Yongsheng yu MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage School of Chemistry and Chemical EngineeringHarbin Institute of TechnologyHarbin 150001HeilongjiangPeople’s Republic of China Space Environment Simulation Research Infrastructure Harbin Institute of TechnologyHarbin 150001People’s Republic of China

ABSTRACT Rationally designing broad-spectrum photocatalysts to harvest whole visible-light region photons and enhance solar energy conversion is a“holy grail”for researchers,but is still a challenging ***,based on the common polymeric carbon nitride(PCN),a hybrid co-catalysts system comprising plasmonic Au nanoparticles(NPs)and atomically dispersed Pt single atoms(PtSAs)with different functions was constructed to address this *** the dual co-catalysts decorated PCN(PtSAs–Au_(2.5)/PCN),the PCN is photoexcited to generate electrons under UV and short-wavelength visible light,and the synergetic Au NPs and PtSAs not only accelerate charge separation and transfer though Schottky junctions and metal-support bond but also act as the co-catalysts for H_(2) ***,the Au NPs absorb long-wavelength visible light owing to its localized surface plasmon resonance,and the adjacent PtSAs trap the plasmonic hot-electrons for H_(2) evolution via direct electron transfer ***,the PtSAs–Au_(2.5)/PCN exhibits excellent broad-spectrum photocatalytic H_(2) evolution activity with the H_(2) evolution rate of 8.8 mmol g^(−1) h^(−1) at 420 nm and 264μmol g^(−1) h^(−1) at 550 nm,much higher than that of Au_(2.5)/PCN and PtSAs–PCN,*** work provides a new strategy to design broad-spectrum photocatalysts for energy conversion reaction.

关键词： Polymeric carbon nitride Au nanoparticles Pt single atoms Photocatalytic H2 evolution Broad-spectrum photocatalysts

Sulfite as the substrate of C-sulfonate metabolism ofα,β-unsaturated carbonyl containing andrographolide:analysis of sulfite in rats'intestinal tract and the reaction kinetics of andrographolide with sulfite

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Chinese Journal of Natural Medicines 2021年第9期19卷 706-712页

作者： HUO Zhi-Peng FENG xin-Chi WANG yu tian yu-Ting QIU Feng School of Chinese Materia Medica and State Key Laboratory of Component-based Chinese MedicineTianjin University of Traditional Chinese MedicineTianjin 301617China ~TCM Research Center Tasly AcademyTasly Holding Group Co.Ltd.Tianjin 300402China State Key Laboratory of Critical Technology in Innovative Chinese Medicine Tasly Pharmaceutical Co.Ltd.Tianjin 300402China Institute of Pharmacy China Pharmaceutical UniversityNanjing 210009China Institute of Pharmaceutical Science and Technology Tianjin UniversityTianjin 300072China

One-sixth of the currently known natural products containα,β-unsaturated carbonyl *** previous studies reported a rare C-sulfonate metabolic *** groups were linked to theβ-carbon ofα,β-unsaturated carbonyl-based natural compounds through this ***,the mechanism of this type of metabolism is still not fully understood,especially whether it is formed through enzyme-mediated biotransformation or direct sulfite *** this work,the enzyme-mediated and non-enzymatic pathways were ***,the sulfite content in rat intestine was determined by LC-MS/*** results showed that the amount of sulfite in rat intestinal contents was from 41.5 to 383μg·g^(-1),whereas the amount of sulfite in rat feed was lower than the lower limit of quantitation(20μg·g^(-1)).Second,the reaction kinetics of sulfite-andrographolide reactions in phosphate buffer solutions(pH 6-8)was *** half-lives of andrographolide ranged from minutes to *** was suggested that the C-sulfonate reaction of andrographolide was very ***,the C-sulfonate metabolites of andrographolide were both detected when andrographolide and L-cysteine-S-conjugate andrographolide were incubated with the rat small intestine contents or sulfite,indicating that the sulfite amount in rat intestine contents was high enough to react with andrographolide,which assisted a significant portion of andrographolide ***,the comparison of andrographolide metabolite profiles among liver homogenate(with NADPH),liver S9(with NADPH),small intestine contents homogenate(with no NADPH),and sulfite solution incubations showed that the C-sulfonate metabolites were predominantly generated in the intestinal tract by non-enzymatic *** summary,sulfite can serve as a substrate for C-sulfonate metabolism,and these results identified non-enzymatically nucleophilic addition as the potential mechanism for C-sulfonate metabolism of compounds containingα,β-unsaturated carbonyl moie

关键词： Sulfite C-Sulfonate metabolites α,β-Unsaturated carbonyl Reaction kinetics Andrographolide Non-enzymatic

On the limit cycles of a quintic planar vector field

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Science China Mathematics 2007年第7期50卷 925-940页

作者： yu-hai WU Li-xin tian Mao-an HAN Department of Mathematics Jiangsu UniversityZhenjiang 212013China Department of Mathematics Shanghai Normal UniversityShanghai 200234China

This paper concerns the number and distributions of limit cycles in a Z 2-equivariant quintic planar vector field. 25 limit cycles are found in this special planar polynomial system and four different configurations of these limit cycles are also given by using the methods of the bifurcation theory and the qualitative analysis of the differential equation. It can be concluded that H(5) ? 25 = 52, where H(5) is the Hilbert number for quintic polynomial systems. The results obtained are useful to study the weakened 16th Hilbert problem.

关键词： double homoclinic loop Melnikov function stability bifurcation limit cycles configuration 34C07 34C23 34C37 37G15

Performance analysis of sign quantized projection

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The Journal of China Universities of Posts and Telecommunications 2010年第1期17卷 62-66页

作者： YE tian-yu NIU xin-xin MA Zhao-feng YANG Yi-xian Information Security Center State Key Laboratory of Networking and Switching Technology Beijing University of Posts and Telecommunications Beijing 100876 China Key Laboratory of Network and Information Attack and Defense Technology of MOE Beijing University of Posts and Telecommunications Beijing 100876 China National Engineering Laboratory for Disaster Backup and Recovery Beijing 100876 China

Quantized projection technology （QP） is the version of quantization index modulation （QIM） working in the projection domain. It essentially belongs to a double-sided additive embedder. In this article, the concept of sign quantized projection （SQP） is proposed, which differs from the conventional QP when working as a single-sided embedder. Theoretical analysis reveals that SQP has the same probability of miss and probability of false alarm as QP. Also, the document-to-watermark ratio （DWR） of SQP is less than its counterpart of QP by lOlg（1＋ γ） dB.

关键词： DWR QP SQP

基于CFD的水力式絮凝工艺结构优化研究进展

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当代化工 2023年第3期52卷 644-649页

作者：王存岩谭竞男田雨欣牟晓蕾烟台大学土木工程学院山东烟台264005

絮凝作为水处理过程中的重要环节,关系到水厂的出水水质。实际工程中水力式絮凝工艺应用广泛,以水流自身能量为絮凝动力条件进行水力搅拌,大大降低了设施运行维护成本。为了研究絮凝流体流动过程中的水力特性,常采用数值模拟方法对絮凝... 详细信息

絮凝作为水处理过程中的重要环节,关系到水厂的出水水质。实际工程中水力式絮凝工艺应用广泛,以水流自身能量为絮凝动力条件进行水力搅拌,大大降低了设施运行维护成本。为了研究絮凝流体流动过程中的水力特性,常采用数值模拟方法对絮凝反应流场进行流态分析。通过有效控制水流的流速及湍动强度改善水动力条件,促进絮凝剂与杂质的混合,进而强化絮凝效果。汇总国内外水力式絮凝工艺的设计应用,系统阐述采用计算流体力学方法进行结构模拟优化方面的研究进展,明确现有数值模拟方法针对絮凝流体流动问题的不足之处,并提出完善工艺的研究方向。

关键词：絮凝池絮凝反应器计算流体力学水力特性

Improved simulation of carbon and water fluxes by assimilating multi-layer soil temperature and moisture into process-based biogeochemical model

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Forest Ecosystems 2019年第2期6卷 87-101页

作者： Min Yan Zengyuan Li xin tian Li Zhang yu Zhou Institute of Remote Sensing and Digital Earth Chinese Academy of Sciences Beijing China Institute of Forest Resource Information Techniques Chinese Academy of Forestry Beijing China Graduate School of Geography Clark University Worcester MA 01610 USA Unstitute of Remote Sensing and Digital Earth Chinese Academy of Sciences Beijing China

Background: Soil temperature and moisture are sensitive indicators in soil organic matter decomposition because they control global carbon and water cycles and their potential feedback to climatic variations. Although the Biome-Biogeochemical Cycles (Biome-BGC) model is broadly applied in simulating forest carbon and water fluxes, its single-layer soil module cannot represent vertical variations in soil moisture. This study introduces the Biome-BGC MuSo model, which is composed of a multi-layer soil module and new modules pertaining to phenology and management for simulations of carbon and water fluxes. Although this model considers soil processes among active layers, estimates of soil-related variables might be biased, leading to inaccurate estimates of carbon and water fluxes. Methods: To improve the estimations of soil-related processes in Biome-BGC MuSo, this study assimilates ground-measured multi-layer daily soil temperature and moisture at the Changbai Mountains forest flux site by using the Ensemble Kalman Filter algorithm. The modeled estimates of water and carbon fluxes were evaluated with measurements using determination coefficient (R2) and root mean square error (RMSE). The differences in the RMSEs from Biome-BGC MuSo and the assimilated Biome-BGC MuSo were calculated (ΔRMSE), and the relationships between ΔRMSE and the climatic and biophysical factors were analyzed. Results: Compared with the original Biome-BGC model, Biome-BGC MuSo improved the simulations of ecosystem respiration (ER), net ecosystem exchange (NEE) and evapotranspiration (ET). Data assimilation of the soil-related variables into Biome-BGC MuSo in real time improved the accuracies of the simulated carbon and water fluxes (ET: R^2=0.81, RMSE=0.70 mm·d^-1;ER: R^2=0.85, RMSE=1.97 gC·m^-2·d^-1;NEE: R^2=0.70, RMSE=1.16 gC·m^-2·d^-1). Conclusions: This study proved that seasonal simulation of carbon and water fluxes are more accurate when using Biome-BGC MuSo with a multi-layer soil module t

关键词： Biome-BGC MuSo Soil temperature Soil moisture Ensemble Kalman filter Data assimilation

DAIS: a method for identifying spatial domains based on density clustering of spatial omics data

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Journal of Genetics and Genomics 2024年第8期51卷 884-887页

作者： Qichao yu Ru tian xin Jin Liang Wu College of Life Sciences University of Chinese Academy of SciencesBeijing 100049China BGI Research ShenzhenGuangdong 518083China BGI ResearchChongqing 401329China BGI Research ShenzhenGuangdong 518083China BGI Research Chongqing 401329China

In multicellular organisms,the spatial arrangement of cells profoundly influences the biological functions of tissues,underscoring the importance of identifying spatial domains in *** advancements in spatial omics,particularly spatial transcriptomics(ST)(Bressan et al.,2023),have enhanced our understanding of tissue spatial organization(Zhang et al.,2022;tian et al.,2023).

关键词： arrangement identifying domains