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A second-order nonlinear optical dendronized hyperbranched polymer containing isolation chromophores： achieving good optical nonlinearity and stability simultaneously

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Science China Chemistry 2018年第5期61卷 584-591页

作者： Haitao Yang Ziyao cheng cheng liu Wenbo Wu Ke-Nan Zhang Shengang Xu Yingliang liu Shaokui Cao Zhen Li School of Materials Science and Engineering Zhengzhou University Zhengzhou 450001 China Department of Chemistry Wuhan University Wuhan 430072 China

Large nonlinear optical(NLO) coefficient and good stability, two essential factors to evaluate second-order NLO materials, are difficult to be achieved in one molecule simultaneously. Herein, by utilizing the concept of "isolation chromophore", "isolation group" and dendritic structure, a dendritic molecule D-NS and a dendronized hyperbranched polymer DHP-NS are prepared to investigate their structure-property relationship. For the small dendritic molecule D-NS, it exhibits a high d33 value of 140 pm/*** this value can be easily dropped when the temperature is higher than 50 °C, which extremely limits its real application. After introducing D-NS into a dendronized hyperbranched polymer chains, the obtained DHP-NS also shows a high d33 value of101 pm/V, but much better stability than D-NS. Even when its thin film was heated to 120 °C, no obvious decay can be observed in the d33 value of DHP-NS. This work demonstrates an effective strategy to realize both large NLO effect and good stability simultaneously.

关键词： nonlinear optical dendritic structure dendronized hyperbranched polymer

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北京南口跨断层流动水准场地监测与布设初探

内陆地震 2017年第3期31卷 290-295页

作者：于海生陆明勇杜建国李宁张金城刘天海寇建新中国地震应急搜救中心北京100049 中国地震局地震预测研究所北京100036

北京南口跨断层流动水准监测场地布设于南口—山前断裂与南口—孙河断裂交汇处。运用前人地质构造研究成果、监测资料和野外地质考察资料等,研究了南口跨断层流动水准场地监测和布设状况、结果表明:(1)监测场地存在未跨断裂测线;(2)4号... 详细信息

北京南口跨断层流动水准监测场地布设于南口—山前断裂与南口—孙河断裂交汇处。运用前人地质构造研究成果、监测资料和野外地质考察资料等,研究了南口跨断层流动水准场地监测和布设状况、结果表明:(1)监测场地存在未跨断裂测线;(2)4号测点不为基岩点且可能在断裂带内;(3)测线巨大突变异常是大量降雨所致,不为前兆异常或断裂活动。

关键词：北京南口跨断层流动水准场地监测与布设

Understanding how charge-charge interaction affects the stereochemistry of enamine fluorination by chiral primary amine catalysis

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中国科学:化学英文版 2023年第10期66卷 2828-2835页

作者： Yanfang Han Kai Yang Long Zhang Sanzhong Luo jin-Pei cheng Center of Basic Molecular Science(CBMS) Department of ChemistryTsinghua UniversityBeijing 100084China Haihe Laboratory of Sustainable Chemical Transformations Tianjin 300192China

Electrostatic interaction, especially electrostatic attraction, usually plays critical roles in controlling the reactivity and selectivity in catalytic transformations;however, the like-charge repulsion, which is ubiquitous in physical systems, is rarely applied in reaction control. Herein we disclosed an unexpected like-charge repulsion induced enantio-control mode in primary aminecatalyzed fluorination reactions with 1-fluoro-2,4,6-trimethylpyridinium triflate. The ionic reaction works favorably in both highly polar(methanol) and non-polar(hexane) solvents, a seldom observed phenomenon in asymmetric catalysis. Erying plot analysis showed that an inversion temperature existed in Me OH, which was explained by the solvent-solute cluster model under different temperatures. Density functional theory(DFT) study and energy decomposition analysis(EDA) verified that the likecharge repulsion takes effect in polar solvent methanol, while in nonpolar solvents, the steric repulsion associated with ion-pair was found to be the major effect for the observed enantioselectivity.

关键词： aminocatalysis fluorination like-charge repulsion iso-inversion temperature ion-pair effect

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带有信息的区间删失数据下AFT模型的参数估计

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数理统计与管理 2024年第1期43卷 58-65页

作者：王淑影刘舒也张亚男程云飞长春工业大学数学与统计学院吉林长春130012

在生存分析研究中,多数文章假定感兴趣的失效时间和删失时间是独立的,但这一假设在实际情况中未必合理。如果忽略失效时间与删失时间的相依性,可能会导致错误的结论。所以本文考虑在带有信息的K型区间删失数据下,采用基于两步估计的极... 详细信息

在生存分析研究中,多数文章假定感兴趣的失效时间和删失时间是独立的,但这一假设在实际情况中未必合理。如果忽略失效时间与删失时间的相依性,可能会导致错误的结论。所以本文考虑在带有信息的K型区间删失数据下,采用基于两步估计的极大似然估计方法对误差项服从标准正态分布的加速失效时间模型(accelerated failure time model,AFT)进行参数估计。同时还进行了数值模拟以验证提出方法的有效性。最后,应用所提出的方法分析艾滋病的临床试验数据。

关键词：加速失效时间模型带有信息的K型区间删失数据极大似然估计法

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基于平滑相机路径的电子稳像算法研究

运筹与模糊学 2024年第3期14卷 188-199页

作者：刘少波金晅宏钟德正上海理工大学光电信息与计算机工程学院上海

在视频拍摄过程中受到环境和人为等因素的影响,拍摄出的视频存在抖动问题。为了解决视频抖动问题,提出了一种基于平滑相机路径的电子稳像方法,使相机运动路径更平滑,同时自适应地对运动补偿后的黑边进行去除,从而获得稳定的视频序列。首... 详细信息

在视频拍摄过程中受到环境和人为等因素的影响,拍摄出的视频存在抖动问题。为了解决视频抖动问题,提出了一种基于平滑相机路径的电子稳像方法,使相机运动路径更平滑,同时自适应地对运动补偿后的黑边进行去除,从而获得稳定的视频序列。首先,对加速稳健特征(SURF)算法进行分区域优化处理,用优化后的SURF算法进行特征点检测,并采用快速视网膜关键点(FREAK)算法对检测到的特征点进行描述;然后基于K近邻匹配(KNN)算法进行特征点对粗匹配,并采用采用随机样本一致性(RANSAC)算法和前向后向匹配算法进行特征点对的二次匹配;最后采用卡尔曼滤波算法优化估计的相机路径,获得更加平滑的相机路径,并采用双线性插值方法对原始视频序列进行运动补偿,以及自适应地去除补偿后视频序列的黑边。所提算法在两类实验场景下相较于原始相机序列的运动路径更加平滑,峰值信噪比(PSNR)值分别提升了4.39dB和4.96dB,从而说明该算法对抖动视频的稳定性和质量均有一定提升。

关键词：电子稳像特征点检测特征点对匹配平滑相机路径运动补偿

强人工智能时代“智能+教师培训”的价值意蕴、现实挑战与突破路径

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现代教育技术 2024年第3期34卷 63-70页

作者：金云波张育桂杨艳刘洪超陕西师范大学教育学部陕西西安710062 信阳师范大学课程与教学改革研究所河南信阳464000 陕西师范大学新闻与传播学院陕西西安710062

在强人工智能时代,“智能+教师培训”的核心价值在于从工具理性的视角出发助力教师不断提升教学水平、发展专业能力,以更好地服务学生成长,然而人工智能技术赋能教师培训的机遇与挑战并存。基于此,文章首先分析了“智能+教师培训”的核... 详细信息

在强人工智能时代,“智能+教师培训”的核心价值在于从工具理性的视角出发助力教师不断提升教学水平、发展专业能力,以更好地服务学生成长,然而人工智能技术赋能教师培训的机遇与挑战并存。基于此,文章首先分析了“智能+教师培训”的核心价值、表现形态与关键应用场景。然后,文章从智能技术发展水平的限制性、培训数据采集的完备性、智能培训系统应用的接受性三个方面,探讨了“智能+教师培训”面临的挑战。最后,文章从做好顶层设计、坚持应用导向、系统组织实施三个维度,提出了“智能+教师培训”可持续发展的突破路径。文章的研究有助于进一步深化“智能+教师培训”的理论探索和实践应用,为人工智能技术赋能高质量的教师专业发展提供参考。

关键词：强人工智能教师培训教育数字化教师专业发展智能技术

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基于压缩态的一维连续变量测量设备无关方案

量子光学学报 2024年第2期30卷 45-57页

作者：刘文元白建东颉琦靳晶晶刘泽慧中北大学半导体与物理学院物理系山西太原030051

测量设备无关协议有效消除了系统中关于探测端的侧信道攻击。一维调制相干态的连续变量量子密钥分发协议具有调制过程简单,成本低和消耗随机数少等特点,其实现条件相比于二维高斯调制更加简单。为了简化实验系统,同时保证较高的安全密... 详细信息

测量设备无关协议有效消除了系统中关于探测端的侧信道攻击。一维调制相干态的连续变量量子密钥分发协议具有调制过程简单,成本低和消耗随机数少等特点,其实现条件相比于二维高斯调制更加简单。为了简化实验系统,同时保证较高的安全密钥速率和传输距离,本文在连续变量量子密钥分发基础上,结合测量设备无关和一维调制相干态协议,提出了基于压缩态的一维调制连续变量测量设备无关协议,详细分析了此方案的实际安全性能,包括传输距离对称和非对称情况。数值仿真结果表明,通过调整调制方差Vm和压缩参数r获得较高安全密钥速率和传输距离,同时分析了加入光源噪声和探测噪声对该方案安全性能的影响机制。这些结果为该方案实验实现提供了理论依据,为进一步简化连续变量量子密钥分发系统实验实现,降低成本,推动系统实用化进程提供了有效途径。

关键词：连续变量量子密钥分发测量设备无关一维高斯调制压缩态

Optimization scheme with pre-processing for cooperative relay multicast networks in cellular system

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The Journal of China Universities of Posts and Telecommunications 2011年第3期18卷 16-21页

作者： WANG cheng-jin LI Xi ZHANG Lin JI Hong Key Laboratory Of Universal Wireless Communication Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 China

For cooperative relay multicast networks, the general cross-layer optimization approaches converge to the global optimal value slowly because of the large quantity of relay terminals. However, the mobility of relay terminals requires quick converging optimization strategies to refresh the relay links frequently. Based on the capacity analysis of multiple relay channels, an improved cross-layer optimization scheme is proposed to resolve this problem, in which the bound of the relay selecting region is determined as a pre-processing. Utilizing the primal-dual algorithm, a cross-layer framework with pre-processing optimizes both the relay terminal selection and power allocation with quick convergence. The simulation results prove the effectiveness of the proposed algorithm.

关键词： cooperative relay cross-layer optimization pre-processing multicast

A 2.5D finite element approach for predicting ground vibrations generated by vertical track irregularities

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2011年第12期12卷 885-894页

作者： Xue-cheng BIAN Chang CHAO Wan-feng jin Yun-min CHEN MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering Department of Civil Engineering Zhejiang University Hangzhou 310058 China

Dynamic responses of track structure and wave propagation in nearby ground vibration become significant when train operates on high speeds. A train-track-ground dynamic interaction analysis model based on the 2.5D finite element method is developed for the prediction of ground vibrations due to vertical track irregularities. The one-quarter car mode,1 is used to represent the train as lumped masses connected by springs. The embankment and the underlying ground are modeled by the 2.5D finite element approach to improve the computation efficiency. The Fourier transform is applied in the direction of train＇s movement to express the wave motion with a wave-number. The one-quarter car model is coupled into the global stiffness matrix describing the track-ground dynamic system with the displacement compatibility condition at the wheel-rail interface, including the irregularities on the track surface. Dynamic responses of the track and ground due to train＇s moving loads are obtained in the wave-number domain by solving the governing equation, using a conventional finite element procedure. The amplitude and wavelength are identified as two major parameters describing track irregularities. The irregularity amplitude has a direct impact on the vertical response for low-speed trains, both for short wavelength and long wavelength irregularities. Track irregularity with shorter wavelength can generate stronger track vibration both for low-speed and high-speed cases. For low-speed case, vibrations induced by track irregularities dominate far field responses. For high-speed case, the wavelength of track irregularities has very little effect on ground vibration at distances far from track center, and train＇s wheel axle weights becomes dominant.

关键词： High-speed railway 2.5D finite element method One-quarter car model Ground vibration Track irregularities