期刊文献+
共找到8,318篇文章
< 1 2 250 >
每页显示 20 50 100
Deformations and extensions of modified λ-differential Lie-Yamaguti algebras
1
作者 TENG Wen PAN Yuewei 《中山大学学报(自然科学版)(中英文)》 北大核心 2025年第4期115-127,共13页
The modifiedλ-differential Lie-Yamaguti algebras are considered,in which a modifiedλ-differential Lie-Yamaguti algebra consisting of a Lie-Yamaguti algebra and a modifiedλ-differential operator.First we introduce t... The modifiedλ-differential Lie-Yamaguti algebras are considered,in which a modifiedλ-differential Lie-Yamaguti algebra consisting of a Lie-Yamaguti algebra and a modifiedλ-differential operator.First we introduce the representation of modifiedλ-differential Lie-Yamaguti algebras.Furthermore,we establish the cohomology of a modifiedλ-differential Lie-Yamaguti algebra with coefficients in a representation.Finally,we investigate the one-parameter formal deformations and Abelian extensions of modifiedλ-differential Lie-Yamaguti algebras using the second cohomology group. 展开更多
关键词 Lie-Yamaguti algebra modifiedλ-differential operator representation and cohomology one-parameter formal deformation Abelian extension
在线阅读 下载PDF
SWAT和WetSpa Extension在罗玉沟流域的应用比较 被引量:2
2
作者 韩旖旎 牛健植 张由松 《水资源与水工程学报》 2014年第3期133-137,共5页
近年来,运用水文模型来研究流域水文状况越来越普遍,本文以黄土高原丘陵沟壑区第三副区的典型小流域为例,基于SWAT和WetSpa Extension两个模型,从模型的输入数据、模型的参数和模型模拟结果等方面进行比较,以期为该区水沙模拟选择合适... 近年来,运用水文模型来研究流域水文状况越来越普遍,本文以黄土高原丘陵沟壑区第三副区的典型小流域为例,基于SWAT和WetSpa Extension两个模型,从模型的输入数据、模型的参数和模型模拟结果等方面进行比较,以期为该区水沙模拟选择合适水文模型并为将来模型性能的改进提供参考。连续15年的校准验证表明:两个模型都能得到较好的结果,而SWAT模型能应用于水文及泥沙等模拟过程,相对来说功能更全面;WetSpa Extension模型目前仅能提供水文模拟的模块,优点在于模拟时间步长较任意,可进行洪水模拟。 展开更多
关键词 SWAT模型 WetSpa extension模型 分布式模型 罗玉沟流域 水文模拟
在线阅读 下载PDF
岩石圈伸展的壳/幔拆离模型(Parallel Extension Tectonics):华北克拉通东部早白垩世岩石圈减薄与破坏机理 被引量:13
3
作者 刘俊来 倪金龙 +4 位作者 陈小宇 Craddock JP 郑媛媛 孙彦琪 季雷 《岩石学报》 SCIE EI CAS CSCD 北大核心 2020年第8期2331-2343,共13页
华北克拉通岩石圈减薄和破坏机理长期以来存在争议,基于岩石学、岩石地球的化学分析研究突出强调深部过程的重要性。前人提出了两种重要模式:包括以拆沉作用为代表的top-down tectonics模型和以热-机械侵蚀与化学侵蚀,或地幔置换、交代... 华北克拉通岩石圈减薄和破坏机理长期以来存在争议,基于岩石学、岩石地球的化学分析研究突出强调深部过程的重要性。前人提出了两种重要模式:包括以拆沉作用为代表的top-down tectonics模型和以热-机械侵蚀与化学侵蚀,或地幔置换、交代作用的bottom-up tectonics模型。然而,对于这两种模式而言尚存在许多无法合理解释的问题,比如在此深部过程中,区域性岩石圈伸展有多大的贡献?地壳伸展构造是作为深部过程的响应,还是同为岩石圈伸展的产物?本文基于早白垩世东亚地区(尤其是华北克拉通东部地区)伸展构造与岩浆活动的综合分析,揭示出华北克拉通东部不同地区伸展构造变形与岩浆活动之间的时、空和成因关系有一定的差异。但整体上看,岩石圈伸展起着主导作用,控制着岩浆上侵和就位,在拆离断层下盘侵入形成各种规模的花岗质为主的侵入体,或于上盘喷发形成火山-沉积岩盆地。在伸展构造发育的不同阶段,可以有伸展早期、伸展期及伸展期后的岩浆活动。岩浆活动的强度及岩浆源区特点有显著的时空变化。一方面,在同一地区不同演化阶段其源区有很大的差异。表现为主体上是早期以古老下地壳源为主,随着壳/幔伸展作用演化,逐渐向混合源或独立幔源的演化。同时,不同地区岩浆源区的变化规律也显著不同。以胶辽地区为例,胶东整体上是壳幔混合源区对于岩浆演化有重要贡献;而辽东地区具有显著的源区演化特点:从剪切早期古老下地壳源区为主,并伴有幔源物质加入,剪切期古老下地壳为主,到剪切晚期和剪切期后以新生下地壳为主。本文认为岩石圈伸展的壳/幔拆离模型(Parallel Extension Tectonics),可以合理地解释华北克拉通及邻区早白垩世构造-岩浆活动性。在该模型中,遭受伸展的华北克拉通岩石圈发生壳-幔拆离作用。在岩石圈伸展作用期间,地壳层次的拆离作用与岩石圈地幔层次上的拆离作用可以是耦合的或者是解耦的,从而导致华北克拉通岩石圈减薄过程中在地壳尺度上的拆离作用与变质核杂岩的剥露有三种不同的类型:同岩浆活动型伸展(C型:Co-magmatism mode extension)、无岩浆活动型伸展(A型:Amagmatism mode extension)和多阶段混合型(M型:Multi-mode extension)。 展开更多
关键词 岩石圈不均匀伸展 壳幔拆离 同伸展岩浆作用 岩石圈伸展的壳幔拆离模型 华北克拉通
在线阅读 下载PDF
Extension集合辨析 被引量:2
4
作者 左静 《郑州工业大学学报》 2001年第2期20-22,共3页
xtension集合是可拓学理论的基础概念之一 .探讨Extension集合的特色和它与其它集合的关系 ,对于明晰可拓学的生存基础、研究价值和发展前景非常重要 .通过比较 3种集合对论域元素的识别与分类原则 ,指出Fuzzy集合Extension集合均以Can... xtension集合是可拓学理论的基础概念之一 .探讨Extension集合的特色和它与其它集合的关系 ,对于明晰可拓学的生存基础、研究价值和发展前景非常重要 .通过比较 3种集合对论域元素的识别与分类原则 ,指出Fuzzy集合Extension集合均以Cantor集合为基础 ,但各自又具有其它集合不可替代的独特之处 .Extension集合的特色在于它对论域元素潜在属性的识别角度和元素属性在特定变换下的可转换性的识别功能 . 展开更多
关键词 extension集合 CANTOR集合 FUZZY集合 可拓学 论域元素 关联函数
在线阅读 下载PDF
Primer Extension-DHPLC检测线粒体DNA 12SrRNA常见耳聋相关突变方法的建立~△ 被引量:3
5
作者 李琦 刘亚青 +3 位作者 孙晨 黄正华 田涛 戴朴 《听力学及言语疾病杂志》 CAS CSCD 北大核心 2019年第2期201-205,共5页
目的建立针对线粒体DNA 12SrRNA基因常见耳聋相关突变的Primer Extension-DHPLC(PE-DHPLC)基因诊断新方法。方法将包含线粒体DNA 12SrRNA 961insC、T1095C、C1494T、A1555G 4种不同突变的4例外周血DNA样本和4例正常对照标本经测序验证,... 目的建立针对线粒体DNA 12SrRNA基因常见耳聋相关突变的Primer Extension-DHPLC(PE-DHPLC)基因诊断新方法。方法将包含线粒体DNA 12SrRNA 961insC、T1095C、C1494T、A1555G 4种不同突变的4例外周血DNA样本和4例正常对照标本经测序验证,PCR扩增靶序列,设计延伸引物,延伸后得到线粒体DNA 12SrRNA基因961insC、T1095C、C1494T、A1555G 4个常见突变的特异性延伸片段,用全变性高效液相色谱分析延伸片段混合物,分离图谱鉴定被检样本的基因型。结果 4例包含线粒体DNA 12SrRNA基因4种耳聋相关突变的DNA样本均扩增出包含4种突变的975 bp特征性条带,PE-DHPLC检测结果显示突变者有引物峰和突变峰两个峰,完全可以鉴别出4种突变,而4例正常对照标本仅显示单个引物峰。结论本实验建立了Primer Extension-DHPLC的线粒体相关耳聋突变分析新方法,可用于耳聋的基因诊断。 展开更多
关键词 线粒体DNA12SrRNA 耳聋 基因突变 变性高效液相色谱 引物延伸
在线阅读 下载PDF
Extension测度和Fuzzy-Extension变换测度及其积分 被引量:2
6
作者 仇计清 《河北轻化工学院学报》 1993年第2期5-11,共7页
提出Extension测度、Extension积分、Fuzzy-Extension变换测度、Fuzzy-Extension变换积分等概念,它们是解决度量领域内不相容问题的重要研究课题。在建立解决量子检测与估值中不相容问题的数学模型方面取得一定进展。
关键词 测度 模糊 扩张 变换 积分
在线阅读 下载PDF
Assessment of bearing performance degradation via extension and EEMD combined approach 被引量:18
7
作者 LIU Yu-mei ZHAO Cong-cong +3 位作者 XIONG Ming-ye ZHAO Ying-hui QIAO Ning-guo TIAN Guang-dong 《Journal of Central South University》 SCIE EI CAS CSCD 2017年第5期1155-1163,共9页
As a key component in rotating machinery, the operating reliability of bearing influences the performance and service life of the equipment directly. In order to describe bearing performance degradation(BPD) process e... As a key component in rotating machinery, the operating reliability of bearing influences the performance and service life of the equipment directly. In order to describe bearing performance degradation(BPD) process effectively, an assessment approach combining extension and ensemble empirical mode decomposition(EEMD) was proposed. First, the extension was utilized to construct the matter-element of bearing operating state, and the energy moment of intrinsic mode functions(IMFs) was used as characteristic parameter of the matter-element. Then, to determine classical domains of characteristic parameters, the mathematical statistics method was adopted. Finally, the BPD was analyzed qualitatively and quantitatively according to the comprehensive correlation degree of bearing current operating state related to its healthy state. The analytic results of bearing test-rig show that the proposed method indicates the incipient fault approximately occurring in the 81 st hour, and the method also quantitatively presents the degree of BPD. By contrast, the BPD assessment based on time-domain features extraction method could not achieve the above two results effectively. 展开更多
关键词 BEARING performance degradation ASSESSMENT extension ENSEMBLE empirical mode decomposition MATHEMATICAL STATISTICS
在线阅读 下载PDF
PETROLOGY AND AGE OF THE KINNAR KAILAS GRANITE:EVIDENCES FOR AN ORDOVICIAN POST-OROGENIC EXTENSION IN THE HIGHER HIMALAYAN CRYSTALLINE, SUTLEJ, INDIA 被引量:3
8
作者 H. S. Chawla\+1, D. Marquer\+1, J. D. Kramers\+2, I. M. Villa\+2, F. Bussy\+3(1 Geological Institute, Emile Argand, 11, 2007, Neuchatel, Switzerland 2 Isotopengeologie, Erlachstrasse 9a, 3012 Bern, Switzerland 3 Institute of Mineralogy and Geochemi 《地学前缘》 EI CAS CSCD 2000年第S1期50-51,共2页
Higher Himalayan Crystalline (HHC) rocks often show metamorphic zonations from lower greenschist facies to migmatites associated with leucogranite intrusions that are classically described as examples of Tertiary inve... Higher Himalayan Crystalline (HHC) rocks often show metamorphic zonations from lower greenschist facies to migmatites associated with leucogranite intrusions that are classically described as examples of Tertiary inverted metamorphism. The present study, based on structural, petrological and geochronological investigations in the Kinnar Kailas Granite (KKG) and surrounding HHC sequence, evidences a discordant intrusive contact of the Ordovician KKG with respect to Pre\|Alpine high grade deformed HHC sequence in the Sutlej valley.Four main phases of deformation are recorded in this HHC sequence and pre\|Ordovician sediments. The first three phases of deformation occurred under high\|grade metamorphic conditions, before the intrusion of the KKG. The geometry of the main progressive ductile deformation (D2—D3) results from SW vergent doming and migmatisation. The latest deformation is expressed by local shearing under greenschist facies conditions. This late D4 deformation corresponds to N—S oriented ductile normal faults lowering the eastern blocks. The KKG is a shallow depth intrusion, showing discordant contacts with the surrounding basement rocks and large scale magmatic stoping. The KKG crosscuts the high\|grade deformation structures (D2—D3) but is locally affected by the local late D4 extensional deformation. The granite textures reflect only slight orientation related to magmatic deformation and even at few centimetres from the intrusion contact, the granite appears undeformed in contrast to the surrounding highly foliated rocks. Furthermore, xenoliths of Kyanite\|Sillimanite bearing basement rocks are present within the KKG. 展开更多
关键词 HIGHER Himalaya CRYSTALLINE GRANITE ORDOVICIAN post\|orogenic extension
在线阅读 下载PDF
Application of extension neural network to safety status pattern recognition of coalmines 被引量:6
9
作者 周玉 W.Pedrycz 钱旭 《Journal of Central South University》 SCIE EI CAS 2011年第3期633-641,共9页
In order to accurately and quickly identify the safety status pattern of coalmines,a new safety status pattern recognition method based on the extension neural network (ENN) was proposed,and the design of structure of... In order to accurately and quickly identify the safety status pattern of coalmines,a new safety status pattern recognition method based on the extension neural network (ENN) was proposed,and the design of structure of network,the rationale of recognition algorithm and the performance of proposed method were discussed in detail.The safety status pattern recognition problem of coalmines can be regard as a classification problem whose features are defined in a range,so using the ENN is most appropriate for this problem.The ENN-based recognition method can use a novel extension distance to measure the similarity between the object to be recognized and the class centers.To demonstrate the effectiveness of the proposed method,a real-world application on the geological safety status pattern recognition of coalmines was tested.Comparative experiments with existing method and other traditional ANN-based methods were conducted.The experimental results show that the proposed ENN-based recognition method can identify the safety status pattern of coalmines accurately with shorter learning time and simpler structure.The experimental results also confirm that the proposed method has a better performance in recognition accuracy,generalization ability and fault-tolerant ability,which are very useful in recognizing the safety status pattern in the process of coal production. 展开更多
关键词 safety status pattern recognition extension neural network coal mines
在线阅读 下载PDF
Feature extension and matching for mobile robot global localization 被引量:1
10
作者 Peng Wang Qibin Zhang Zonghai Chen 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 2015年第4期840-846,共7页
This paper introduces an indoor global localization method by extending and matching features. In the proposed method, the environment is partitioned into convex subdivisions. Local extended maps of the subdivisions a... This paper introduces an indoor global localization method by extending and matching features. In the proposed method, the environment is partitioned into convex subdivisions. Local extended maps of the subdivisions are then built by exten- ding features to constitute the local extended map set. While the robot is moving in the environment, the local extended map of the current local environment is established and then matched with the local extended map set. Therefore, global localization in an indoor environment can be achieved by integrating the position and ori- entation matching rates. Both theoretical analysis and comparison experimental result are provided to verify the effectiveness of the proposed method for global localization. 展开更多
关键词 feature extension global localization feature match-ing mobile robot.
在线阅读 下载PDF
Application of extension method to fault diagnosis of transformer 被引量:4
11
作者 邓宏贵 曹建 +1 位作者 罗安 夏向阳 《Journal of Central South University of Technology》 EI 2007年第1期88-93,共6页
A novel extension diagnosis method was proposed for enhancing the diagnosis ability of the conventional dissolved gas analysis. Based on the extension theory a matter-element model was established for qualitatively an... A novel extension diagnosis method was proposed for enhancing the diagnosis ability of the conventional dissolved gas analysis. Based on the extension theory a matter-element model was established for qualitatively and quantitatively describing the fault diagnosis problem of power transformers. The degree of relation based on the dependent functions was employed to determine the nature and the grade of the faults in a transformer system. And the proposed method was verified with the experimental data. The results show that accuracy rate of the diagnosis method exceeds 90% and two kinds of faults can be detected at the same time. 展开更多
关键词 power transformer fault diagnosis extension theory matter-element model dependent function
在线阅读 下载PDF
Structural integrity and life extension of high-temperature components
12
作者 汪淳 沈士明 《Journal of Central South University》 SCIE EI CAS 2005年第S2期45-52,共8页
Four different topics for high-temperature components, namely the development of the assessment codes for the structural integrity of high-temperature components, the application of continuous damage mechanics and pro... Four different topics for high-temperature components, namely the development of the assessment codes for the structural integrity of high-temperature components, the application of continuous damage mechanics and probabilistic damage mode on the life assessment of high-temperature components, the life extension for high-temperature components and a proposed strategy for remanufacturing of high-temperature components were discussed in this paper. These topics should provide some important insights for the design and re-design of high- temperature components. 展开更多
关键词 INTEGRITY LIFE extension COMPONENT REMANUFACTURING CREEP
在线阅读 下载PDF
Acceptability of Bush Meat as a Source of Animal Protein in Delta State, Nigeria: Implication for Extension Services
13
作者 Ebewore S O Ovharhe O J Emaziye P O 《Journal of Northeast Agricultural University(English Edition)》 CAS 2015年第3期67-78,共12页
The study examined the acceptability ofhnsh meat to Deltans. The specific objectives were to ascertain the consumption pattern of bush meat; identify the major types of bush meat consumed in the area; determine the li... The study examined the acceptability ofhnsh meat to Deltans. The specific objectives were to ascertain the consumption pattern of bush meat; identify the major types of bush meat consumed in the area; determine the likely constraints to bush meat consumption; and stipulate the extension implication of the findings. A systematic sampling technique was used to compose a sample size of 410 respondents. Data used for this study were collected using well structured interview schedule and data were analyzed using descriptive statistical techniques such as tables, percentages, means and standard deviation, and inferential statistics (linear regression model). The result of the study indicated that almost all the respondents (402) representing about 98% was formally consuming bush meat. The findings also revealed that as many as 323 individuals, representing 78.8% of the respondents did not consume bush meat currently. Only about 12.7% and 8.5% occasionally and regularly consumed bush meat respectively. It was therefore very obvious that people no longer consumed bush meat in Delta state as before. The results further indicated that the predominant bush meat consumed in the area were cane rat (97.70%) and the African giant snails (Achatina and Archachatina) (94.25%). The result of the multiple regression analyses indicated that the coefficient for education (X3), income (Xs), Ebola (X6) and availability of game (XT) were significant at 5%, indicating that these variables were important factors influencing the consumption of bush meat in the study area. However, the coefficients of education level and Ebola factor were negative and significant, suggesting respondents with higher education and aware of Ebola disease were not likely to consume bush meat. As the result, it was concluded that bush meat was now almost unacceptable due to several factors like dread of Ebola disease, unavailability of game, educational level and income, which significantly affected the consumption of bush meat. It was therefore recommended among others that extension delivery services on how to domesticate game species should be available to farmers. 展开更多
关键词 game ACCEPTABILITY EBOLA extension Cane rat DELTA NIGERIA
在线阅读 下载PDF
改进邻域扩展A^(*)算法的移动机器人路径规划 被引量:1
14
作者 董雅文 杨静雯 +1 位作者 张宝锋 赵小惠 《机械设计与制造》 北大核心 2025年第1期291-295,共5页
为解决A^(*)算法在规划路径时存在转折角度过大、路径不平滑的问题,提出改进邻域扩展A^(*)算法。首先,对A^(*)算法搜索范围扩展至24邻域,然后对邻域进行二次数量优化处理得到最终邻域搜索节点。其次,设计具有双层位置导向信息的评价函数... 为解决A^(*)算法在规划路径时存在转折角度过大、路径不平滑的问题,提出改进邻域扩展A^(*)算法。首先,对A^(*)算法搜索范围扩展至24邻域,然后对邻域进行二次数量优化处理得到最终邻域搜索节点。其次,设计具有双层位置导向信息的评价函数,最后对所得路径进行二次平滑处理以剔除冗余节点并削弱路径尖峰的剧烈程度。仿真结果表明,改进邻域扩展A^(*)算法在路径长度、搜索节点数量、规划时间上均优于传统A^(*)算法,且路径无尖峰转角,整体趋势平缓。 展开更多
关键词 点对点路径规划 A^(*)算法 邻域扩展
在线阅读 下载PDF
基于组合赋权和物元可拓模型的东北河流健康评价 被引量:1
15
作者 张媛媛 刘建卫 +1 位作者 逄晓腾 王明玮 《中国农村水利水电》 北大核心 2025年第2期31-36,44,共7页
为构建适用于东北地区的河流健康评价体系,针对东北河流特殊的季节性冰封水文特征,以及传统评价体系的应用局限性,如未给予水文指标合理的权重和解释,评价结果难以体现河流健康发展趋势等问题。基于《河湖健康评估技术导则(SL/T793-2020... 为构建适用于东北地区的河流健康评价体系,针对东北河流特殊的季节性冰封水文特征,以及传统评价体系的应用局限性,如未给予水文指标合理的权重和解释,评价结果难以体现河流健康发展趋势等问题。基于《河湖健康评估技术导则(SL/T793-2020)》,结合东北河流的水文、生态和社会服务功能等多维特征进行评价体系及方法改进,并以拉林河、第二松花江、伊通河、饮马河、东辽河等东北典型河流作为研究对象,通过采用组合赋权和物元可拓模型的方法,对各河流的健康等级进行量化评价,并利用综合关联度距离预测了河流健康水平的未来发展趋势。结果显示,改进后的东北河流健康评价体系共包含水文、水环境、河岸物理结构、水生生物以及社会服务功能5个状态层16项评价指标,能够基本适应东北河流的健康评价需求;健康评价结果得到伊通河最大综合关联度为0.014 6,健康等级为IV级,处于“不健康”状态,其余河流均处于“亚健康”状态(III级),且健康状态呈好转趋势。这一结论在综合指数法和模糊评价模型中得到了验证,能够为东北河流的持续健康管理提供科学依据,同时,也为类似寒冷地区的河流健康评估和管理提供了参考。 展开更多
关键词 河流健康 指标体系 组合赋权法 物元可拓
在线阅读 下载PDF
大兴安岭南段黄岗梁地区早白垩世正长花岗岩成因及构造启示:锆石U−Pb年龄、岩石地球化学和Sr−Nd−Pb同位素证据 被引量:2
16
作者 顾玉超 陈仁义 +1 位作者 杜继宇 鞠楠 《地质通报》 北大核心 2025年第1期91-116,共26页
【研究目的】大兴安岭南段黄岗梁锡铁矿区及外围发育大面积花岗岩类,加强其成岩时代、岩石成因类型、成岩成矿物质来源等研究,有利于探究该区成岩与成矿关系和早白垩世碰撞造山机制。【研究方法】采集大兴安岭南段黄岗梁锡铁矿区及外围... 【研究目的】大兴安岭南段黄岗梁锡铁矿区及外围发育大面积花岗岩类,加强其成岩时代、岩石成因类型、成岩成矿物质来源等研究,有利于探究该区成岩与成矿关系和早白垩世碰撞造山机制。【研究方法】采集大兴安岭南段黄岗梁锡铁矿区及外围样品,进行岩相学、锆石U−Pb测年、岩石地球化学及Rb−Sr、Sm−Nd、Pb同位素研究。【研究结果】获得岩浆结晶年龄为141.9~139.1 Ma,较成矿年龄早约3 Ma,形成于早白垩世。岩石具有高硅、低铝、低镁、富钾少钠特征,为高钾钙碱性A型花岗岩。(^(87)Sr/^(86)Sr)_(i)和^(143)Nd/^(144)Nd值分别介于0.70031~0.70543和0.512572~0.512636之间,ε_(Nd)(t)值为0.07~1.18,Nd同位素模式年龄T_(DM2)为926~838 Ma。【结论】黄岗梁矽卡岩型锡铁矿床成岩物质于新元古代从亏损地幔分离,在上升侵位过程中受到地壳物质混染。大兴安岭南段地区在早白垩世经历了蒙古–鄂霍次克洋碰撞闭合伸展作用和古太平洋高角度俯冲作用叠加。 展开更多
关键词 Sr−Nd−Pb同位素 花岗岩 碰撞后伸展环境 锆石U−Pb年龄 黄岗梁地区 大兴安岭
在线阅读 下载PDF
我国学前教育优质均衡的探索历程、反思与展望 被引量:1
17
作者 邓泽军 钱孝兵 《河北师范大学学报(教育科学版)》 北大核心 2025年第1期124-132,共9页
随着高质量学前教育体系建设的持续推进,我国学前教育正朝着优质均衡的目标迈进,推动了相关研究的持续深入。通过对相关文献的系统梳理,发现我国学前教育大致经历了重点关注“规模发展”、全面关注“均衡发展”、转向关注“优质均衡”... 随着高质量学前教育体系建设的持续推进,我国学前教育正朝着优质均衡的目标迈进,推动了相关研究的持续深入。通过对相关文献的系统梳理,发现我国学前教育大致经历了重点关注“规模发展”、全面关注“均衡发展”、转向关注“优质均衡”三大阶段,并且各阶段研究普遍比较丰硕。但是,相关研究探索尚未形成系统、多元、特色的研究体系,主要局限于研究特色趋同、交叉研究不足、实证研究欠缺、指标体系缺乏等方面。后续研究需要超越单一层面的重复探索,走向更具独特性、多视域、针对性、可行性的策略体系创新,立足县域管理,从静态关注转向动态发展探索;重视政策优化,从单一均衡转向多元视角的优质均衡关注;着眼实践成效,从外延式均衡转向内涵式优质均衡关注;聚焦路径创新,从发散式关注转向聚焦式优质均衡探索。 展开更多
关键词 学前教育高质量发展 外延式均衡发展 内涵式优质均衡
在线阅读 下载PDF
有限性与延展性:新中国国家安全思想的演进
18
作者 祁昊天 赵书韫 《国际安全研究》 北大核心 2025年第1期73-95,157,共24页
文章从国家安全本体论、安全体系认识论与安全实践方法论三个维度考察新中国的国家安全思想,以社会主义革命和建设时期、改革开放和社会主义现代化建设新时期以及中国特色社会主义新时代进行时间分段,讨论新中国国家安全思想的演进。有... 文章从国家安全本体论、安全体系认识论与安全实践方法论三个维度考察新中国的国家安全思想,以社会主义革命和建设时期、改革开放和社会主义现代化建设新时期以及中国特色社会主义新时代进行时间分段,讨论新中国国家安全思想的演进。有限性与延展性是这一演进过程中安全思想的连贯体现,分别涵盖了安全目标、认知与方法在各阶段静态与动态、横向与纵向的特征。虽然新中国在不同时期面临不同的安全环境和安全需求,安全形势愈加复杂,但是安全思想和实践总体符合安全有限、延展演进的特征。安全具有弹性但不可过载,不存在绝对安全的空间,而狭义的、单一领域或维度的安全亦无法有效支撑对国家安全的维护,特别是在愈加复杂和不确定的国家安全环境中更是如此。新中国国家安全思想“有限—延展”的演进特征反映了安全环境的客观变化与领导人主观能动的决策部署。 展开更多
关键词 国家安全思想 演进 有限性 延展性
在线阅读 下载PDF
基于扩展式博弈的组网雷达功率分配方法研究
19
作者 叶方 戚昌龙 +1 位作者 孙柳晴 李一兵 《电子与信息学报》 北大核心 2025年第6期1803-1815,共13页
组网雷达已成为对抗电子干扰的重要手段,然而随着干扰机集群化智能化发展,组网雷达在突防对抗中只能观测到部分信息,严重影响了对突防目标的检测性能。针对上述问题,该文提出一种基于扩展式博弈的组网雷达功率分配方法。该方法首先构造... 组网雷达已成为对抗电子干扰的重要手段,然而随着干扰机集群化智能化发展,组网雷达在突防对抗中只能观测到部分信息,严重影响了对突防目标的检测性能。针对上述问题,该文提出一种基于扩展式博弈的组网雷达功率分配方法。该方法首先构造了组网雷达功率分配和对抗信息缺失模型,并结合扩展式博弈原理,建立了面向功率分配的扩展式博弈模型,在该博弈中,组网雷达可以通过信息集聚合对抗中不可观测的干扰机信息。在求解该文所构建博弈模型时,采用深度虚拟遗憾最小化算法(Deep CFR),其通过结合深度学习与虚拟遗憾最小化,有效解决了传统方法在求解扩展式博弈中的存储与计算瓶颈。仿真结果表明,所提方法在部分观测信息约束条件下能有效对组网雷达进行功率分配,提高其对突防目标的检测概率。 展开更多
关键词 组网雷达系统 扩展式博弈 功率分配
在线阅读 下载PDF
空间光学遥感相机伸展支撑机构设计与分析
20
作者 王庆雷 陈亚新 +5 位作者 张鑫 杨路伟 孙德伟 黄巧林 史创 蔺宇辉 《中国空间科学技术(中英文)》 北大核心 2025年第2期94-102,共9页
相机伸展机构展开锁定后需要能够获得并保持足够的刚度及尺寸稳定性,同时针对特定空间光学遥感相机高精度高展收比的需求,设计了一种采用高刚度涡卷弹簧来实现铰链间隙消除及展开后结构高刚度保持的一维空间光学遥感相机高精度高展收比... 相机伸展机构展开锁定后需要能够获得并保持足够的刚度及尺寸稳定性,同时针对特定空间光学遥感相机高精度高展收比的需求,设计了一种采用高刚度涡卷弹簧来实现铰链间隙消除及展开后结构高刚度保持的一维空间光学遥感相机高精度高展收比伸展支撑机构。该伸展支撑机构采用涡卷弹簧驱动折展杆来实现机构展开,控速机构控制展开速度,展开后通过铰链定位面定位,涡卷弹簧剩余驱动力和张力索保持刚度。开展了伸展支撑机构的展开动力学分析、模态分析、考虑构件长度误差与铰链回转间隙的展开精度分析、工作环境下的热变形分析。设计完成相机伸展支撑机构,该机构展开基频在20 Hz以上,对伸展机构样机进行了地面重复展收精度测量,展开精度优于±0.05 mm,伸展支撑机构性能良好,满足空间光学遥感相机特殊任务需求。 展开更多
关键词 伸展支撑机构 动力学 模态分析 精度分析 重复展收精度测量
在线阅读 下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部