检索结果-南通市图书馆

China Foundry 2025年第1期22卷 75-82页

作者： lin-fei xia Wen-bo Li Zuo-shan Wei Yu-ying Wu xiang-fa Liu China Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials Ministry of EducationShandong UniversityJinan 250061China Shandong Key Laboratory of Advanced Aluminum Materials and Technology Binzhou Institute of TechnologyBinzhou 256600ShandongChina

Near-eutectic Al-Si alloys are widely used in automotive manufacturing due to their superior wear resistance and high temperature *** of high Si content,the grain refinement of near-eutectic Al-Si alloy has been a problem for many *** this study,the effect of deep cryogenic treatment(DCT)on the microstructure and mechanical properties of Al-12Si-4Cu-2Ni-Mg alloy with addition of Al-Ti-C-B master alloy was fully *** show that the average grain size of the alloy is greatly reduced from 0.92 mm to 0.50 mm,and the eutectic Si and Al7Cu4Ni precipitates are spheroidized and refined in Al-12Si-4Cu-2Ni-Mg after DCT for 24 h and aging *** these changes of microstructures result in a significant increment of about 22.5%in elongation and a slight enhancement of about 6.8%in tensile ***,the refinement of microstructure also significantly improves the fatigue life of the alloy.

关键词： deep cryogenic treatment near-eutectic Al-Si master alloy microstructure mechanical properties

价值·挑战·路向:高校服务全民终身学习的发展逻辑

在线全文

学校读者我要写书评

暂无评论

成人教育 2025年第2期45卷 23-27页

作者：张博林宝霞黑龙江大学哈尔滨150080 哈尔滨科学技术职业学院哈尔滨150300

高校服务全民终身学习是落实教育强国发展战略、建设学习型社会、实现教育现代化的重要举措。面对数字化转型契机,高校服务全民终身学习迎来了服务职能、服务机制与服务方式的现实挑战。亟须以教育全民性、教育终身性与教育共享性作为... 详细信息

高校服务全民终身学习是落实教育强国发展战略、建设学习型社会、实现教育现代化的重要举措。面对数字化转型契机,高校服务全民终身学习迎来了服务职能、服务机制与服务方式的现实挑战。亟须以教育全民性、教育终身性与教育共享性作为高校服务全民终身学习的逻辑起点,结合高校教学、科研、社会服务的基本职能,不同类型教育与不同形式教育的建设机制,以及多元主体共享开放的服务方式,探索高校服务全民终身学习的实践路向,构建现代化全民终身学习教育体系。

关键词：全民终身学习教育数字化高校

在线全文

学校读者我要写书评

暂无评论

汽车碰撞相容性的影响因素及优化策略研究

机械设计与制造工程 2025年第1期54卷 124-128页

作者：夏麟上海开放大学嘉定分校上海201800

针对移动渐进可变形壁障(MPDB)工况下汽车碰撞相容性的影响因素及优化策略设计问题,介绍了MPDB工况碰撞试验相容性评价规程,建立了MPDB工况碰撞试验模型,从碰撞加速度、碰撞能量以及碰撞变形等方面进行了分析,阐明了质量、两车速度差以... 详细信息

针对移动渐进可变形壁障(MPDB)工况下汽车碰撞相容性的影响因素及优化策略设计问题,介绍了MPDB工况碰撞试验相容性评价规程,建立了MPDB工况碰撞试验模型,从碰撞加速度、碰撞能量以及碰撞变形等方面进行了分析,阐明了质量、两车速度差以及相对刚度等参数对相关指标的影响规律,从整备质量、碰撞面积、刚度分布以及增加能量传递路径等角度提出了4种优化策略,并对相关方案进行了模型仿真验证。结果表明:碰撞过程中能量分布不均匀是影响相容性的主要因素,单纯地降低整备质量、增大碰撞接触面积、优化刚度分布等都能对相容性有一定改善,但不及增加能量传递路径明显。

关键词：相容性移动渐进可变形壁障碰撞模型能量传递路径

针对星钟跳变的北斗三号卫星自主时间同步算法

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

国防科技大学学报 2025年第1期47卷 222-229页

作者：周黎莎林宝军邵瑞强林夏任前义贺红雨孙建锋田艳中国科学院空天信息创新研究院北京100094 中国科学院大学北京100049 中国科学院微小卫星创新研究院上海201304 上海微小卫星工程中心上海201210 中国科学院上海光学精密机械研究所上海201800

针对星钟异常跳变引起的星上时间与整网星座时间偏离的问题,设计了一种针对星钟跳变的北斗三号卫星自主时间同步算法。通过引入抗差最小二乘估计,对分布式星座时间同步算法进行改进,使其具有快速检测钟差异常跳变并具有自主时间同步的... 详细信息

针对星钟异常跳变引起的星上时间与整网星座时间偏离的问题,设计了一种针对星钟跳变的北斗三号卫星自主时间同步算法。通过引入抗差最小二乘估计,对分布式星座时间同步算法进行改进,使其具有快速检测钟差异常跳变并具有自主时间同步的能力。采用与北斗三号卫星一致的仿真环境,并引入实际在轨测试数据,对算法进行了准确评估。结果表明在60 d内,星座各星时间同步误差不超过3.68 ns,且当卫星产生跳变异常后,该算法可在1h内恢复时间同步,提高了算法在钟跳下的可靠性。

关键词：北斗三号卫星导航系统星钟跳变星间链路时间同步

Stahel-Donoho kernel estimation for fixed design nonparametric regression models

在线全文

学校读者我要写书评

暂无评论

Science China Mathematics 2006年第12期49卷 1879-1896页

作者： lin Lu CUI xia School of Mathematics and System Sciences Shandong UniversityJi'nan 250100China School of Mathematics and System SciencesShandong UniversityJi'nan 250100China

This paper reports a robust kernel estimation for fixed design nonparametric regression models.A Stahel-Donoho kernel estimation is introduced,in which the weight functions depend on both the depths of data and the distances between the design points and the estimation *** on a local approximation,a computational technique is given to approximate to the incomputable depths of the *** a result the new estimator is computationally *** proposed estimator attains a high breakdown point and has perfect asymptotic behaviors such as the asymptotic normality and convergence in the mean squared *** the depth-weighted estimator for parametric regression models,this depth-weighted nonparametric estimator has a simple variance structure and then we can compare its efficiency with the original *** simulations show that the new method can smooth the regression estimation and achieve some desirable balances between robustness and efficiency.

关键词： nonparametric regression,kernel estimation,statistical depth,robustness.

Robust UKF orbit determination method with timevarying forgetting factor for angle/range-based integrated navigation system

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第11期37卷 420-434页

作者： Qichang QIANG Baojun lin Yingchun LIU xia lin Shen WANG Innovation Academy for Microsatellites of Chinese Academy of Sciences Shanghai 201203China School of Electronic Electrical and Communication EngineeringUniversity of Chinese Academy of SciencesBeijing 100049China Shanghai Engineering Center for Microsatellites Shanghai 201203China School of Information Science and Technology Shanghai Tech UniversityShanghai 201210China

The angle/range-based integrated navigation system is a favorable navigation solution for deep space ***,the statistical characteristics of the measurement noise are time-varying,leading to inaccuracies in the derived measurement covariance even causing filter *** reduce the gap between theoretical and actual covariances,some adaptive methods use empirically determined and unchanged forgetting factors to scale innovations within the sliding ***,the constant weighting sequence cannot accurately adapt to the time-varying measurement noise in dynamic ***,this paper proposes an Adaptive Robust Unscented Kalman Filter with Time-varying forgetting factors(TFF-ARUKF)for the angle/range integrated navigation ***,based on a statistically linear regression model approximating the nonlinear measurement model,the M-estimator is adopted to suppress the interference of ***,the covariance matching method is combined with the Huber linear regression problem to adaptively adjust the measurement noise covariance used in the ***,to capture the time-varying characteristics of the measurement noise in each estimation,a new timevarying forgetting factors selection strategy is designed to dynamically adjust the adaptive matrix used in the covariance matching *** and experimental analysis compared with EKF,AMUKF,ARUKF,and Student's t-based methods have validated the effectiveness and robustness of the proposed algorithm.

关键词： Autonomous navigation Integrated navigation system State estimation Kalman filter Adaptive filter

The effects of ion screening on neutrino-nucleus interactions in core-collapse supernova explosions

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2010年第7期10卷 689-695页

作者： Xiong-Ping xia lin Yi Department of Physics Huazhong University of Science and Technology Wuhan 430074 China

The effects of ion screening in stellar core collapses are investigated based on a new progenitor star model. Simulation results show that ion screening slightly affects the leptons and decreases explosion energy, which is a negative factor for energy transfer supernova explosions. We also investigate the effect on type Ⅱ-supernova explosions of neutrino-nucleus elastic scattering based on the new progenitor star model. It is shown that, compared with the previously calculated results, neutrinos-nucleus elastic scattering in stellar core collapses is more severe, leading to an obvious reduction of the neutrino leakage energy loss and an increase of supernova explosion energy.

关键词： stars supernovae general -- neutrino-nucleus

乙二醇产品塔全回流和侧采产品液相加氢的工业化应用

在线全文

学校读者我要写书评

暂无评论

现代化工 2025年第2期45卷 243-248,254页

作者：林晓霞刘景刚王建平新疆生产建设兵团天盈石油化工股份有限公司新疆阿拉尔843300 合肥江新化工科技有限公司安徽合肥230601

为提高聚酯级乙二醇收率,同时提高乙二醇产品质量,新疆天盈石化实施了乙二醇液相加氢技改项目,首次设计了2种操作工况,分别为乙二醇产品塔全回流液相加氢工况和乙二醇产品塔侧采产品液相加氢工况。工业化运行结果表明,在2种工况下,液相... 详细信息

为提高聚酯级乙二醇收率,同时提高乙二醇产品质量,新疆天盈石化实施了乙二醇液相加氢技改项目,首次设计了2种操作工况,分别为乙二醇产品塔全回流液相加氢工况和乙二醇产品塔侧采产品液相加氢工况。工业化运行结果表明,在2种工况下,液相加氢提高紫外透光率和降低醛含量效果明显,聚酯级乙二醇收率均提高至100%;在全回流液相加氢工况下,回流液和侧采产品的紫外透光率得到了提升,且降低了醛含量;在侧采液相加氢工况下,液相加氢后乙二醇产品紫外透光率、醛含量、含水率和轻组分指标均能达到聚酯级指标要求。

关键词：液相加氢天然气制乙二醇全回流液相加氢侧采产品液相加氢

同方期刊数据库

Exclusive Semileptonic Rare Decays B→K()(?)+(?)^- in a Top Quark Two-Higgs-Doublet Model

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2008年第7期50卷 149-160页

作者： LV lin-xia xiaO Zhen-Jun Department of Physics Nanyang Teacher＇s College Nanyang 473061 China Department of Physics and Institute of Theoretical Physics Nanjing Normal University Nanjing 210097 China

Employing improved calculations of the decay form factors from light-cone sum rules, we evaluate the invariant mass spectrum, forward-backward asymmetry, and lepton polarizations of the exclusive processes B → K^（＊）e＋e- in the SM and T2HDM. From the recent measurements of their branching ratios, we find that these processes do provide additional bounds on the new parameters in the model considered here. After the inclusion of the new physics contributions, the large enhancement of FBA, which is unobservably small within the SM and of the lepton polarization at large tan β, may precisely test the SM or reveal new physics in forthcoming accurate experiments.

关键词： semileptonic decay two-Higgs-doublet model polarization forward-backward asymmetry

Travel Patterns Analysis of Urban Residents Using Automated Fare Collection System

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Electronics 2016年第1期25卷 40-47页

作者： WANG Ya DU Bowen RONG Qiannan lin xia State Key Laboratory of Software Development Environment Beihang University School of Software Beihang University

As one of the essential information, passenger Origin-destination(OD) matrix is crucial for transit system planning. Automated fare collection(AFC) system is widely used in big cities all around the world, OD data not only can be collected in dynamic way but also through citywide. It is only a byproduct of AFC and have the imperfection. This paper proposes a novel method to infer trip chain information of each commuter’s OD matrix based on travel pattern identify, and then the relationship between lines which have the character of the geographical proximity is used to calibrate the result of inferring. A serious of experiment results based on the real data show that the method has relatively high accuracy and can be use to practical application.

关键词： Smart card Public transportation Travel patterns