检索结果-南通市图书馆

An object correlation and maneuver detection approach for space surveillance

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2012年第10期12卷 1402-1416页

作者： Jian Huang Wei-Dong Hu Qin xin xiao-yong du ATR Key Lab. College of Electronic Science and Engineering National University of DefenseTechnology Changsha 410073 China Faculty of Science and Technology University of the Faroe Islands Torshavn FO100 FaroeIslands

Object correlation and maneuver detection are persistent problems in space surveillance and maintenance of a space object catalog. We integrate these two prob- lems into one interrelated problem, and consider them simultaneously under a sce- nario where space objects only perform a single in-track orbital maneuver during the time intervals between observations. We mathematically formulate this integrated sce- nario as a maximum a posteriori （MAP） estimation. In this work, we propose a novel approach to solve the MAP estimation. More precisely, the corresponding posterior probability of an orbital maneuver and a joint association event can be approximated by the Joint Probabilistic Data Association （JPDA） algorithm. Subsequently, the ma- neuvering parameters are estimated by optimally solving the constrained non-linear least squares iterative process based on the second-order cone programming （SOCP） algorithm. The desired solution is derived according to the MAP criterions. The per- formance and advantages of the proposed approach have been shown by both theoret- ical analysis and simulation results. We hope that our work will stimulate future work on space surveillance and maintenance of a space object catalog.

关键词： celestial mechanics -- methods: analytical -- techniques: miscellaneous-- surveys

De novo synthesis of atropisomeric benzofurans via Cu/SPDO complex catalyzed asymmetric formal[3+2]annulation

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2025年第1期68卷 174-180页

作者： Fan-xiao Meng Xing-Yu Wang Ka Lu Ju-Song Yang Fu-Min Zhang Ai-Jun Ma Bao du yong-Qiang Tu State Key Laboratory of Applied Organic Chemistry College of Chemistry and Chemical EngineeringLanzhou UniversityLanzhou 730000China School of Chemistry and Chemical Engineering Shanghai Jiao Tong UniversityShanghai 200240China School of Biotechnology and Health Sciences Wuyi UniversityJiangmen 529020China

Herein,the de novo synthesis of atropisomeric benzofurans through the Cu/spirocyclic-pyrrolidine-oxazoline(SPDO)complex catalyze asymmetric formal[3+2]cycloaddition between quinones and ynamides is explored,producing a range of structurally diverse axially chiral benzofurans in satisfactory yields with good to excellent ***,density functional theory calculations were applied to explain the possible reaction mechanism.

关键词： benzofuran atropisomers novel de novo synthetic strategy asymmetric formal[3+2]cycladdition Cu/SPDO complex DFT calculations

The Hilbert expansion of the Boltzmann equation in the incompressible Euler level in a channel

在线全文

学校读者我要写书评

暂无评论

Science China Mathematics 2025年第1期68卷 39-88页

作者： Feimin Huang Weiqiang Wang yong Wang Feng xiao Academy of Mathematics and Systems Science Chinese Academy of SciencesBeijing 100190China School of Mathematical Sciences University of Chinese Academy of SciencesBeijing 100049China Key Laboratory of Computing and Stochastic Mathematics(Ministry of Education) School of Mathematics and StatisticsHunan Normal UniversityChangsha 410081China

The study of the hydrodynamic limit of the Boltzmann equation with physical boundary is a challenging problem due to the appearance of the viscous and Knudsen boundary *** this paper,the hydrodynamic limit from the Boltzmann equation with the specular reflection boundary condition to the incompressible Euler equations in a channel is *** on the multi-scaled Hilbert expansion,the equations with boundary conditions and compatibility conditions for interior solutions,and viscous and Knudsen boundary layers are derived under different scaling,***,some uniform estimates for the interior solutions,and viscous and Knudsen boundary layers are *** the help of the L^(2)-L^(∞) framework and the uniform estimates obtained above,the solutions to the Boltzmann equation are constructed by the truncated Hilbert expansion with multiscales,and hence the hydrodynamic limit in the incompressible Euler level is justified.

关键词： Boltzmann equation incompressible Euler equations hydrodynamic limit Hilbert expansion specular reflection boundary condition viscous boundary layer Knudsen boundary layer

Atomic-scale insights into microscopic mechanisms of grain boundary segregation in Al−Cu alloys

在线全文

学校读者我要写书评

暂无评论

Transactions of Nonferrous Metals Society of China 2025年第1期35卷 1-12页

作者： Xiong SHUAI Hong MAO Sai TANG Yi KONG yong du State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China College of Mechanical Engineering Hunan Institute of Science and TechnologyYueyang 414006China National Key Laboratory of Science and Technology on High-strength Structural Materials Central South UniversityChangsha 410083China

This study aims to clarify the mechanisms for the grain boundary(GB)segregation through investigating the absorption of excess solute atoms at GBs in Al−Cu alloys by using the hybrid molecular dynamics/Monte Carlo *** segregation mechanisms,substitutional and interstitial mechanisms,are *** intergranular defects,including dislocations,steps and vacancies,and the intervals in structural units are conductive to the prevalence of interstitial *** substitutional mechanism is favored by the highly ordered twin ***,the two mechanisms affect the GB structure *** is quantified that interstitial mechanism is less destructive to GB structure than substitutional one,and often leads to a segregation level being up to about 6 times higher than the *** findings contribute to atomic scale insights into the microscopic mechanisms about how solute atoms are absorbed by GB structures,and clarify the correlation among intergranular structures,segregation mechanisms and kinetics.

关键词： grain boundaries segregation Al−Cu alloy intergranular structure molecular dynamics simulation Monte Carlo simulation

平面不规则RC框剪结构基于性能的减震设计方法

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

工程力学 2017年第3期34卷 68-75页

作者：黄小宁杜永峰李慧兰州理工大学防震减灾研究所兰州730050 兰州理工大学西部土木工程防灾减灾教育部工程研究中心兰州730050

在引入最不利输入角度的基础上,运用改进的基于多模态推覆分析法对平面不规则RC框剪结构进行减震设计。首先,利用MATLAB小波变换系数法,判别地震动的最不利输入角度;然后,根据结构提出的性能目标,以多模态推覆分析的设计方法为主,结合... 详细信息

在引入最不利输入角度的基础上,运用改进的基于多模态推覆分析法对平面不规则RC框剪结构进行减震设计。首先,利用MATLAB小波变换系数法,判别地震动的最不利输入角度;然后,根据结构提出的性能目标,以多模态推覆分析的设计方法为主,结合能力谱法计算结构所需的附加阻尼比,选择相应的粘滞阻尼器,合理布置阻尼器的位置;最后,利用扭转角能力法对比分析原结构和减震结构的抗扭性能。分析结果表明:对于平面不规则RC框剪结构,地震动输入角度对结构的抗震性能有不可忽略的影响;利用改进的基于多模态推覆分析法对结构进行减震设计后可达到预先提出的性能目标,减小结构的扭转位移比,提高结构的抗震性能。

关键词：平面不规则RC框剪结构减震结构小波变换多模态扭转角能力法

维普期刊数据库博看期刊

Potential preservative mechanisms of cardiac rehabilitation pathways on endothelial function in coronary heart disease

在线全文

学校读者我要写书评

暂无评论

Science China(Life Sciences) 2025年第1期68卷 158-175页

作者： Wen-Tao Sun Jian-yong du Jia Wang Yi-Long Wang Er-Dan Dong Research Center for Cardiopulmonary Rehabilitation University of Health and Rehabilitation Sciences Qingdao Hospital(Qingdao Municipal Hospital)Schoolof Health and Life SciencesUniversityof Health and Rehabilitation SciencesQingdao 266071China Department of Cardiology and Instituteof Vascular Medicine Peking University Third HospitalTheInstituteofCardiovascular SciencesPeking UniversityState Key Laboratoryof Vascular Homeostasisand RemodelingPeking UniversityBeijing 100191China

Cardiac rehabilitation,a comprehensive exercise-based lifestyle and medical management,is effective in decreasing morbidity and improving life quality in patients with coronary heart *** function,an irreplaceable indicator in coronary heart disease progression,is measured by various methods in traditional cardiac rehabilitation pathways,including medicinal treatment,aerobic training,and smoking ***,studies on the effect of some emerging cardiac rehabilitation programs on endothelial function are *** article briefly reviewed the endothelium-beneficial effects of different cardiac rehabilitation pathways,including exercise training,lifestyle modification and psychological intervention in patients with coronary heart disease,and related experimental models,and summarized both uncovered and potential cellular and molecular mechanisms of the beneficial roles of various cardiac rehabilitation pathways on endothelial *** exercise training and some lifestyle interventions,the enhanced bioavailability of nitric oxide,increased circulating endothelial progenitor cells(EPCs),and decreased oxidative stress are major contributors to preventing endothelial dysfunction in coronary heart ***,the preservation of endothelial-dependent hyperpolarizing factors and inflammatory suppression play *** the one hand,to develop more endothelium-protective rehabilitation methods in coronary heart disease,adequately designed and sized randomized multicenter clinical trials should be advanced using standardized cardiac rehabilitation programs and existing assessment *** the other hand,additional studies using suitable experimental models are warranted to elucidate the relationship between some new interventions and endothelial protection in both macro-and microvasculature.

关键词： cardiac rehabilitation coronary heart disease endothelial function

Improvement of charge-transfer kinetics via MXene and cobalt containing polyoxometalate loading on CdS for photocatalytic hydrogen production

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2025年第2期68卷 772-780页

作者： Yu Feng xiao Fang Jinnuo Zang Bin Song Chunlian Hu xiaoyu Dong yong Ding State Key Laboratory of Applied Organic Chemistry Key Laboratory of Advanced Catalysis of Gansu ProvinceCollege of Chemistry and Chemical EngineeringLanzhou UniversityLanzhou 730000China State Key Laboratory of Low Carbon Catalysis and Carbon Dioxide Utilization State Key Laboratory for Oxo Synthesis and Selective OxidationLanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000China

Hydrogen is a renewable and clean energy,and photocatalytic water splitting for hydrogen evolution technology is a promising technical means to solve the development *** this study,the ternary composite Co_(8)POM@MXene–CdS hybrid catalyst was constructed and used for photocatalytic hydrogen *** the condition of AM 1.5G simulated sunlight,the photocatalytic H_(2) evolution rate of the ternary composite was 8.13 mmol g^(−1) h^(−1),which was more than 25 times higher than that of the bare *** means of synchronous illumination X-ray photoelectron spectroscopy(SI-XPS)and density functional theory(DFT)calculations,it was proved that the loading of MXene and Co_(8)POM improved the photogenerated carrier separation and immigration efficiency on *** photogenerated electrons transfer from CdS to ***_(8)POM containing the{Co_(4)O_(3)}quasi-cubane,as an oxidation co-catalyst,accepts photogenerated holes from CdS to catalyze the oxidation reaction of TEOA,which improves the photocatalytic hydrogen production activity and the stability of CdS.

关键词： CdS polyoxometalates MXene hybrid catalyst photocatalytic hydrogen evolution

Context-Aware Semantic Type Identification for Relational Attributes

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Computer Science & Technology 2023年第4期38卷 927-946页

作者：丁玥郭雨荷卢卫李海翔张美慧李晖潘安群杜小勇 Key Laboratory of Data Engineering and Knowledge Engineering of Ministry of Education Renmin University of China Beijing 100872China School of Information Renmin University of ChinaBeijing 100872China Tencent(Beijing)Technology Company Limited Beijing 100080China School of Computer Science and Technology Beijing Institute of TechnologyBeijing 100081China College of Computer Science and Technology Guizhou UniversityGuiyang 550025China Tencent(Shenzhen)Technology Company Limited Shenzhen 518057China

Identifying semantic types for attributes in relations,known as attribute semantic type(AST)identification,plays an important role in many data analysis tasks,such as data cleaning,schema matching,and keyword search in ***,due to a lack of unified naming standards across prevalent information systems(*** islands),AST identification still remains as an open *** tackle this problem,we propose a context-aware method to figure out the ASTs for relations in this *** transform the AST identification into a multi-class classification problem and propose a schema context aware(SCA)model to learn the representation from a collection of relations associated with attribute values and schema *** on the learned representation,we predict the AST for a given attribute from an underlying relation,wherein the predicted AST is mapped to one of the labeled *** improve the performance for AST identification,especially for the case that the predicted semantic types of attributes are not included in the labeled ASTs,we then introduce knowledge base embeddings(***)to enhance the above representation and construct a schema context aware model with knowledge base enhanced(SCA-KB)to get a stable and robust *** experiments based on real datasets demonstrate that our context-aware method outperforms the state-of-the-art approaches by a large margin,up to 6.14%and 25.17%in terms of macro average F1 score,and up to 0.28%and 9.56%in terms of weighted F1 score over high-quality and low-quality datasets respectively.

关键词： attribute semantic type(AST)identification context-aware semantic embedding knowledge base embedding

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

企业营销网络的有效性与稳定性分析

数学的实践与认识 2017年第18期47卷 8-15页

作者：秦效宏杜永红西京学院经济管理系陕西西安710123

实际的企业营销网络往往有着巨大而且复杂的网络结构,这种结构影响甚至支配着企业营销网络的运作.在经典经济研究思想的基础上,吸收复杂网络的有关概念和研究方法,提出企业营销网络的稳定性和有效性的定义,依据效用理论建立企业营销网... 详细信息

实际的企业营销网络往往有着巨大而且复杂的网络结构,这种结构影响甚至支配着企业营销网络的运作.在经典经济研究思想的基础上,吸收复杂网络的有关概念和研究方法,提出企业营销网络的稳定性和有效性的定义,依据效用理论建立企业营销网络内生形成模型,分析有效和稳定的企业营销网络具有的特征.并通过算列进行说明.研究结论可为企业建设与管理营销网络提供理论指导.

关键词：企业营销网络内生模型有效性稳定性