检索结果-南通市图书馆

Even and Odd Coherent States for Time-Dependent Harmonic Oscillator

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2002年第7期38卷 25-30页

作者： WEI Lian-Fu YANG qing-yi WANG Shun-Jin Department of Physics Shanghai Jiao Tong University Shanghai 200030 China Department of Physics Guangxi University Nanning 530003 China Institute of Physics Southwest Jiao Tong University Chengdu 610031 China Department of Modern Physics Lanzhou University Lanzhou 730000 China

The dynamical invariant for a general time-dependent harmonic oscillator is constructed by making use of two linearly independent solutions to the classical equation of motion. In terms of this dynamical invariant we define the time-dependent creation and annihilation operators and relevantly introduce even and odd coherent states for time dependent harmonic oscillator. The mathematical and quantum statistical properties of these states are discussed in detail. The harmonic oscillator with periodically varying frequency is treated as a demonstration of our general approach.

关键词： even and odd coherent states, time-dependent harmonic oscillator, dynamical invariant

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

某泵站液压闸门开度仪技术升级改造及应用

水电站机电技术 2024年第3期47卷 84-86页

作者：李宝李庆义赵谦李君南水北调东线山东干线有限责任公司山东济南250109

根据南水北调东线八里湾泵站液压闸门开度仪精确度达不到要求的现状,阐述了对液压闸门开度仪进行技术升级改造的背景,系统的提出液压闸门开度仪技术升级改造内容并进行实施应用,通过进行技术升级改造使液压闸门开度仪的精确度大大提升,... 详细信息

根据南水北调东线八里湾泵站液压闸门开度仪精确度达不到要求的现状,阐述了对液压闸门开度仪进行技术升级改造的背景,系统的提出液压闸门开度仪技术升级改造内容并进行实施应用,通过进行技术升级改造使液压闸门开度仪的精确度大大提升,完全满足机组启动要求,实现了预期应用效果。

关键词：南水北调八里湾泵站液压闸门开度仪升级改造效果应用

在线全文

学校读者我要写书评

暂无评论

深圳市创新空间结构测度与影响因素分析

广州大学学报（自然科学版） 2024年第3期23卷 82-92页

作者：王玉娇千庆兰陈清怡杨娜广州大学地理科学与遥感学院广东广州510006 华南理工大学建筑学院广东广州510641

作为创新活动的重要载体,创新空间是近年来创新地理学领域关注的重点内容。文章将深圳市创新空间划分技术型、知识型和孵化型3类,结合创新企业数据、POI数据和统计年鉴等数据类型,通过核密度估计、DBSCAN聚类算法以及MGWR模型等方法,刻... 详细信息

作为创新活动的重要载体,创新空间是近年来创新地理学领域关注的重点内容。文章将深圳市创新空间划分技术型、知识型和孵化型3类,结合创新企业数据、POI数据和统计年鉴等数据类型,通过核密度估计、DBSCAN聚类算法以及MGWR模型等方法,刻画创新空间的结构特征、各自异同点及其影响因素。研究发现:①深圳市技术型、知识型和孵化型创新空间均表现为“中心—外围”圈层特点,其中,技术型创新空间还具有等级性组团结构特征;②地区创新水平、产业园支持、金融咨询服务、交通发达程度以及某些生活服务和公共服务会显著正向促进创新空间集聚,但综合型创新核心区、专业型创新发展区和潜力型创新成长区受到的影响具有差异性。基于研究结论,文章针对性地提出了优化深圳市创新空间的政策建议,以期为城市创新空间的优化提供依据。

关键词：创新空间结构特征影响因素 DBSCAN空间聚类 MGWR

基于DeepLabV3+模型的轨道站点影响区自行车出行环境评价

在线全文

学校读者我要写书评

暂无评论

科学技术与工程 2024年第10期24卷 4300-4306页

作者：朱震军张芮嘉张勇过秀成韩吉徐逸清南京林业大学汽车与交通工程学院南京210037 东南大学交通学院南京211189

轨道站点影响区自行车出行环境评价对于促进自行车接驳出行效率和服务品质提升具有重要意义。采集百度街景、路网、轨道站点等多源数据,选取自行车出行环境的舒适性、安全性、便捷性和可达性评价指标,运用DeepLabV3+模型和sDNA分析法对... 详细信息

轨道站点影响区自行车出行环境评价对于促进自行车接驳出行效率和服务品质提升具有重要意义。采集百度街景、路网、轨道站点等多源数据,选取自行车出行环境的舒适性、安全性、便捷性和可达性评价指标,运用DeepLabV3+模型和sDNA分析法对轨道站点1500 m范围影响区内不同类型道路的自行车出行环境进行评价,并以南京市为例进行实证分析。结果表明:站点影响区自行车出行环境存在空间差异性;交通型道路的自行车出行中间性、天空可视度高,但自行车存取方便程度低;生活型道路的自行车存取方便程度、绿视率高,但自行车出行中间性、安全性低;综合型道路各指标相对协调。

关键词：轨道站点影响区自行车出行 DeepLabV3+模型出行环境评价

Preparation, Properties and Mechanism of Inhomogeneous Calcium Alginate Ion Cross-linking Gel Microspheres

在线全文

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2003年第1期19卷 85-88页

作者： CHEN yi qing SUN Duo xian LIU Jun HUANG Ya qing School of Chemical Engineering and Technology Tianjin UniversityTianjin 300072P.R.China

Inhomogeneous calcium alginate ion cross\|linking gel microspheres, a novel ion absorbent, were prepared by dropping a sodium alginate solution to a calcium chloride solution via an electronic droplet generator. Calcium alginate microspheres have uniform particle sizes, a smooth surface and a microporous structure. The electrode probe reveals the inhomogeneous distribution of calcium ions with the highest concentration on the surface, and the lowest concentration in the cores of the spheres. As a novel ion adsorbent, calcium alginate gel microspheres have a lower limiting adsorption mass concentration, a higher enrichment capacity and a higher adsorption capacity for Pb 2+ than usual ion exchange resins. The highest percentage of the adsorption is 99 79%. The limiting adsorption mass concentration is 0 0426 mg/L. The adsorption capacity for Pb 2+ is 644 mg/g. Calcium alginate gel microspheres have a much faster ion exchange velocity than D418 chelating resin and D113 polyacrylate resin. The moving boundary model was employed to interpret the ion exchange kinetics process, which indicates that the ion exchange process is controlled by intraparticle diffusion of adsorbable ions. So the formation of inhomogeneous gel microspheres reduces the diffusion distance of adsorbable ions within the spheres and enhances the ion exchange velocity. Alginate has a higher selectivity for Pb 2+ than for Ca 2+ and the selectivity coefficient K Pb Ca is 316. As an ion cross\|linking gel, calcium alginate inhomogeneous microspheres can effectively adsorb heavy metal Pb 2+ at a higher selectivity and a higher adsorption velocity. It is a novel and good ion adsorbent.

关键词： Alginate Inhomogeneous microsphere Adsorption Mechanism

Groundwater System Division and Description of Asia

在线全文

学校读者我要写书评

暂无评论

Acta Geologica Sinica(English Edition) 2016年第4期90卷 1434-1443页

作者： ZHANG Fawang yi qing CHENG Yanpei YUE Chen DONG Hua Institute of Karst Geology Chinese Academy of Geological Sciences Institute of Hydrogeology and Environmental Geology Chinese Academy of Geological Sciences

Based on landform, climate, river system, geological structure and hydrogeological structure and from the perspective of systematology, the groundwater system of Asia can be divided into 36 secondary groundwater systems under 11 primary ones by the intercontinental scale. This forms part of the work of the groundwater series map of Asia, which is compiled according to groundwater system division and evaluation of the total amount and types of aquifer, reflecting the large-scale features of groundwater resources in Asia. Systematic profiling of groundwater in this way provides a scientific basis for groundwater exploitation planning and management in Asia, and avoiding disputes over groundwater resources and the environment among Asian countries.

关键词： Asia groundwater system climate and topography division

Techniques for increasing the yield of stem cell-derived exosomes:what factors may be involved?

在线全文

学校读者我要写书评

暂无评论

Science China(Life Sciences) 2022年第7期65卷 1325-1341页

作者： Zi-Yuan Feng qing-yi Zhang Jie Tan Hui-Qi Xie Laboratory of Stem Cell and Tissue Engineering Orthopedic Research InstituteMed-X Center for MaterialsState Key Laboratory of BiotherapyWest China HospitalSichuan UniversityChengdu 610041China

Exosomes are nano-scale extracellular vesicles secreted by cells and constitute an important part in the cell-cell *** main contents of the exosomes include proteins,micro RNAs,and *** mechanism and safety of stem cell-derived exosomes have rendered them a promising therapeutic strategy for regenerative ***,limited yield has restrained full explication of their functions and clinical *** address this,various attempts have been made to explore the up-and down-stream manipulations in a bid to increase the production of *** review has recapitulated factors which may influence the yield of stem cell-derived exosomes,including selection and culture of stem cells,isolation and preservation of the exosomes,and development of artificial exosomes.

关键词： exosome stem cell yield therapy

A new numerical model of ring shear tester for shear band soil considering friction-induced thermal pressurization

在线全文

学校读者我要写书评

暂无评论

Journal of Mountain Science 2022年第11期19卷 3302-3313页

作者： ZHAO Neng-hao SONG Kun ZHANG Rong-tang yi qing-lin School of Civil Engineering and Architecture Wuhan Polytechnic UniversityWuhan 430023China Key Laboratory of Geological Hazards on Three Gorges Reservoir Area(China Three Gorges University) Ministry of EducationYichang 443002China

In this study,a new numerical model of ring shear tester for shear band soil of landslide was *** special feature of this model is that it considers the mechanism of friction-induced thermal pressurization,which is potentially an important cause of high-speed catastrophic *** key to the construction of this numerical ring shear model is to realize the THM(thermo-hydro-mechanical)dynamic coupling of soil particles,which includes the processes of frictional heating,thermal pressurization,and strength softening during shearing of solid *** of these are completed by using discrete element *** on this new model,the characteristics of shear stress change with shear displacement,as well as the variation of temperature and pore pressure in the specimen,are studied at shear rates of 0.055 m/s,0.06 m/s,0.109 m/s and 1.09 m/s,*** results show that the peak strength and residual strength of specimen are significantly reduced when the mechanism of frictioninduced thermal pressurization is *** greater the shear rate is,the higher the temperature as well as the pore pressure *** effect of shear rate on the shear strength is *** simulation results demonstrate that this model can effectively simulate the mechanism of friction-induced thermal pressurization of shear band soil during ring shear process,and the shear strength softening in the *** new numerical ring shear model established in this study is of great significance for studying the dynamic mechanism of high-speed catastrophic landslides.

关键词： Ring shear model Discrete element method THM coupling Frictional heating Thermal pressurization

基于随机动态规划的热带草原气候灌区种植结构优化研究

在线全文

学校读者我要写书评

暂无评论

节水灌溉 2024年第10期 15-21页

作者：张昊赵升伟钱俊毛劲乔张培培龚轶青河海大学水利水电学院南京210098 长江设计集团有限公司武汉430014 长江国际工程设计有限公司北京100032

为了降低热带草原气候区域可用水资源不确定性带来的灌区规划风险,合理进行灌区农作物的种植结构分配,从而充分发挥灌区经济效益,结合确定性动态规划及随机规划的优点,建立了基于随机动态规划的热带草原气候灌区种植结构优化模型。以塞... 详细信息

为了降低热带草原气候区域可用水资源不确定性带来的灌区规划风险,合理进行灌区农作物的种植结构分配,从而充分发挥灌区经济效益,结合确定性动态规划及随机规划的优点,建立了基于随机动态规划的热带草原气候灌区种植结构优化模型。以塞内加尔卢加灌区为例,通过分析长系列1987-2016年灌区的灌溉可用水量,建立正态分布概率函数进行概率模拟,将随机动态规划模型应用于卢加灌区并将试验结果与确定性动态规划模型结果进行对比。研究结果表明,随机动态规划模型能够充分考虑灌区灌溉可用水量的不确定性,对灌区种植结构进行合理优化,相较于确定性动态规划的种植结构结果,平均每年增加1.37亿CFA的经济效益;随机动态规划模型的种植结构规划结果能够有效应对干旱等极端气候条件带来的影响,在极端干旱时(如1987年)灌区经济效益较确定性动态规划增加5.33亿CFA,使灌区发挥较高且稳定的经济效益。研究成果有利于灌区制定合理的农田管理和种植决策,为灌区农业经济可持续发展提供科学依据。

关键词：热带草原气候灌区种植结构优化动态规划随机动态规划灌溉可用水量的不确定性

同方期刊数据库博看期刊