期刊文献+
共找到21篇文章
< 1 2 >
每页显示 20 50 100
Kinetic Studies on Aniline-catalyzed Carbohydrate Oxime Formation via Real-time NMR
1
作者 WANG Wen-jun CAO Chen-ming +2 位作者 JIN Chen WANG Xin WANG George-peng 《Chemical Research in Chinese Universities》 SCIE CAS CSCD 2011年第5期886-890,共5页
The authors investigated an aniline-catalyzed method to accelerate the reaction between equimolar reducing glycans and hydroxylamines. The rate-constants determined by real-time NMR were associated with the equivalenc... The authors investigated an aniline-catalyzed method to accelerate the reaction between equimolar reducing glycans and hydroxylamines. The rate-constants determined by real-time NMR were associated with the equivalence ratio of aniline rather than the concentration. Conjugates of oligosaccharide with hydroxylamine can be obtained in high efficiency at pH=5.4. 展开更多
关键词 GLYCOCONJUGATE ANILINE CATALYSIS kinetics real-time NMR
下载PDF
基于星载GPS数据的HY-2B卫星简化动力学精密定轨
2
作者 齐鑫敏 王建波 +3 位作者 贾永君 张龙平 郭金运 纪兵 《海洋测绘》 CSCD 北大核心 2023年第3期45-48,63,共5页
为研究满足HY-2B星载GPS定轨要求的EGM2008重力场模型合理阶次和HY-2B卫星简化动力学定轨精度,采用HY-2B卫星14天星载GPS观测数据及不同阶次EGM2008重力场,进行简化动力学轨道确定。结果表明:采用120阶及以上阶次的EGM2008重力场模型,... 为研究满足HY-2B星载GPS定轨要求的EGM2008重力场模型合理阶次和HY-2B卫星简化动力学定轨精度,采用HY-2B卫星14天星载GPS观测数据及不同阶次EGM2008重力场,进行简化动力学轨道确定。结果表明:采用120阶及以上阶次的EGM2008重力场模型,能够获得厘米级高精度定轨结果。同时,检核结果显示:采用简化动力学法定轨时,载波相位残差结果稳定在6.2~6.8mm之间,重叠轨道对比结果在轨道径向、切向、法向上均优于0.6cm,SLR检核整体轨道精度优于4cm。定轨结果满足测高卫星需求,可为后续我国海洋系列卫星精密轨道确定等相关科学研究提供借鉴。 展开更多
关键词 低轨卫星 星载gps 精密定轨 简化动力学 卫星激光测距(SLR)
下载PDF
黄河口海域测验中GPS动态后处理技术的应用 被引量:2
3
作者 霍瑞敬 宋士强 田慧 《人民黄河》 CAS 北大核心 2016年第1期9-11,18,共4页
为了解决黄河口海域测验中远距离数据传输的问题,利用精密星历代替广播星历,采用GPS 动态后处理技术取代数字传输技术,得到了不同基线长度测点的三维坐标值.在90 km 范围之内,与GPS-RTK 模式获取的数据相比,GPS动态后处理技术处理得到... 为了解决黄河口海域测验中远距离数据传输的问题,利用精密星历代替广播星历,采用GPS 动态后处理技术取代数字传输技术,得到了不同基线长度测点的三维坐标值.在90 km 范围之内,与GPS-RTK 模式获取的数据相比,GPS动态后处理技术处理得到的高程数据误差最大为0.167 m,平均误差为0.007~0.047 m,中误差在0.064 m 以内,误差的变化与基线长度基本呈正比,远小于传统的潮汐改正误差;测点平面点位数据误差最大不超过0.097 m,平均误差为0.004~0.031 m,中误差不超过0.037 m,其变化趋势和基线长度没有明显的关系,也远小于信标机的定位误差. 展开更多
关键词 gps动态后处理技术 精密星历 gps-RTK 海域测验 黄河口
下载PDF
手持GPS和罗盘仪在涉案林地面积测量中的精度分析 被引量:14
4
作者 张民侠 张运生 +1 位作者 郑怀兵 唐静 《中南林业调查规划》 2009年第1期61-64,共4页
通过在南京中山陵风景区不同林地条件下及南京森林公安学校校园内选设的多个点进行面积测量,以全站仪测量结果为真值,对比分析手持GPS和罗盘仪在林地面积测量中的精度问题,为森林公安人员在办理森林案件中测算林地面积提供参考。
关键词 林地面积 测量精度 实时动态gps 罗盘仪 全站仪
下载PDF
基于RTK功能的GPS道路中线测设原理与试验 被引量:3
5
作者 冯晓 周平 +2 位作者 范洪成 武学强 曹志翔 《重庆交通学院学报》 2002年第4期75-78,共4页
介绍了GPS实时动态定位 (RTK)技术的基本原理 ,一种新的基于RTK功能的高斯平面坐标的GPS道路中线测设的原理方法 ,其中包括使用线元法解决任意复杂曲线的多种中桩点里程定义问题 ,以及区线的测设一体化技术 .
关键词 中线测设 原理 试验 全球卫星定位系统 gps 实时动态定位 RTK 路线测量 道路工程
下载PDF
Precise Point Positioning Technique with IGS Real-Time Service (RTS) for Maritime Applications 被引量:2
6
作者 Mohammed El-Diasty Mohamed Elsobeiey 《Positioning》 2015年第4期71-80,共10页
The maritime navigation accuracy requirements for radionavigation systems such as GPS are specified by the International Maritime Organization (IMO). Maritime navigation usually consists of three major phases identifi... The maritime navigation accuracy requirements for radionavigation systems such as GPS are specified by the International Maritime Organization (IMO). Maritime navigation usually consists of three major phases identified as Ocean/Coastal/Port approach/Inland waterway, in port navigation and automatic docking with an accuracy requirement that ranges from 10 m to 0.1 m. With the advancement in autonomous GPS positioning techniques such as Precise Point Positioning (PPP) and with the advent of the new IGS-Real-Time-Service (RTS), it is necessary to assess the possibility of a wider role of the PPP-based positioning technique in maritime applications. This paper investigates the performance of an autonomous real-time PPP-positioning solution by using the IGS- RTS service for maritime applications that require an accurate positioning system. To examine the performance of the real-time IGS-RTS PPP-based technique for maritime applications, kinematic data from a dual frequency GPS receiver is investigated. It is shown that the real-time IGS-RTS PPP-based GPS positioning technique fulfills IMO requirements for maritime applications with an accuracy requirement ranges from 10 m for Ocean/Coastal/Port approach/Inland waterways navigation to 1.0 m for in port navigation but cannot fulfill the automatic docking application with an accuracy requirement of 0.10 m. To further investigate the real-time PPP-based GPS positioning technique, a comparison is made between the real-time IGS-RTS PPP-based positioning technique and the real-time PPP-based positioning by using the predicted part of the IGS Ultra-Rapid products and the real-time GPS positioning technique with the Wide Area Differential GPS service (WADGPS). It is shown that the IGS-RTS PPP-based positioning technique is superior to the IGS-Ultra-Rapid PPP-based and WADGPS-based positioning techniques. 展开更多
关键词 real-time Service RTS MARITIME NAVIGATION IGS gps IMO Ultra-Rapid WADgps
下载PDF
应用GPS网络RTK技术建立区域性空间定位动态服务体系的几点思考 被引量:12
7
作者 林良光 《东北测绘》 2002年第3期41-42,共2页
对GPS网络RTK技术作简要介绍 ,分析传统技术的不足 ,说明该技术在建立区域性空间定位动态服务体系等各方面的应用。
关键词 VRS gps网络RTK技术 空间定位动态服务 虚拟参考站 全球定位系统
下载PDF
Real-Time Optimization Model for Continuous Reforming Regenerator
8
作者 Jiang Shubao Jiang Hongbo +1 位作者 Li Zhenming Tian Jianhui 《China Petroleum Processing & Petrochemical Technology》 SCIE CAS 2021年第3期90-103,共14页
An approach for the simulation and optimization of continuous catalyst-regenerative process of reforming is proposed in this paper.Compared to traditional method such as finite difference method,the orthogonal colloca... An approach for the simulation and optimization of continuous catalyst-regenerative process of reforming is proposed in this paper.Compared to traditional method such as finite difference method,the orthogonal collocation method is less time-consuming and more accurate,which can meet the requirement of real-time optimization(RTO).In this paper,the equation-oriented method combined with the orthogonal collocation method and the finite difference method is adopted to build the RTO model for catalytic reforming regenerator.The orthogonal collocation method was adopted to discretize the differential equations and sequential quadratic programming(SQP)algorithm was used to solve the algebraic equations.The rate constants,active energy and reaction order were estimated,with the sum of relative errors between actual value and simulated value serving as optimization objective function.The model can quickly predict the fields of component concentration,temperature and pressure inside the regenerator under different conditions,as well as the real-time optimized conditions for industrial reforming regenerator. 展开更多
关键词 catalytic reforming regenerator kineticS model orthogonal collocation method real-time optimization
下载PDF
南黄海辐射沙脊群海域GPS-PPK海测方案应用分析 被引量:3
9
作者 张颖 沈卫明 +1 位作者 李静 赵刚 《现代测绘》 2019年第3期46-48,共3页
为解决南黄海辐射沙脊群海域独特地理、水文条件下水深测量的现实困难,提高测量精度,本文将GPS动态后处理技术(GPS-PPK)运用于该海域的水下地形测量工作中。GPS-PPK技术具有控制距离远、无需实时数据传输的优点,是船载一体化水深测量时... 为解决南黄海辐射沙脊群海域独特地理、水文条件下水深测量的现实困难,提高测量精度,本文将GPS动态后处理技术(GPS-PPK)运用于该海域的水下地形测量工作中。GPS-PPK技术具有控制距离远、无需实时数据传输的优点,是船载一体化水深测量时三维精确定位的理想选择。本文在数据结构、GPS-PPK信号频谱定量分析的基础上,提出了GPS-PPK截频滤波及数据匹配方案,使其适用于该海区水深测量并进一步提高测量精度。实验表明,整套方案操作便捷、有效可靠,测量精度较传统验潮方案更高。同时,远距离无验潮测量,节省了大量人力物力,非常值得在广阔的南黄海辐射沙脊群海域浅水环境下推广使用。 展开更多
关键词 南黄海辐射沙脊群 gps动态后处理技术 水深测量 数值滤波
下载PDF
GPS Workstation—A Static Point Averaging and Tracks Mapping Application
10
作者 Khalid Amin Khan Gulraiz Akhter 《Positioning》 2013年第1期57-64,共8页
This paper describes GPS Workstation, a general purpose navigation software which requires a low-cost GPS connected to the computer. It provides an integrated display of positioning data along with satellite positions... This paper describes GPS Workstation, a general purpose navigation software which requires a low-cost GPS connected to the computer. It provides an integrated display of positioning data along with satellite positions, their signal strengths and data quality parameters. The software can be used for static point averaging of GPS data to get more precise positioning and real-time mapping of roads and tracks. It supports output of data in keyhole markup language (KML) as well as other formats for visualization of acquired data on Google Earth and geographic information systems. It can also be used to determine geo-referencing errors in Google Earth imagery for an area and can compensate the error by applying a constant X, Y shift. The software is available for distribution under the free software license. 展开更多
关键词 gps real-time MAPPING Google EARTH Data AVERAGING
下载PDF
BDS/GPS非组合动态定位性能分析
11
作者 吴磊 《工程勘察》 2018年第5期64-67,共4页
研究了非组合观测值长距离RTK定位,将对流层延迟和电离层延迟参数化,并附加合理的动力学方程约束,将解算模型统一到卡尔曼滤波中。介绍了RTK定位中的若干问题的处理方法,对BDS,GPS,BDS+GPS的长距离RTK定位性能进行了初步评估,验证了RTK... 研究了非组合观测值长距离RTK定位,将对流层延迟和电离层延迟参数化,并附加合理的动力学方程约束,将解算模型统一到卡尔曼滤波中。介绍了RTK定位中的若干问题的处理方法,对BDS,GPS,BDS+GPS的长距离RTK定位性能进行了初步评估,验证了RTK的收敛时间受到可视卫星数和卫星几何构形的影响,长基线情况下单系统RTK模糊度初始化时间不少于5min,双系统模糊度初始化时间约为2min。BDS,GPS单系统RTK平面定位精度均在3cm以内,而BDS+GPS双系统RTK平面定位结果在2cm以内,且双系统高程方向定位精度略优于单系统。 展开更多
关键词 卡尔曼滤波 动力学模型 非组合RTK BDS/gps
下载PDF
异功散中人参皂苷类成分在脾虚大鼠模型肠吸收动力学变化及其陈皮的影响 被引量:1
12
作者 沈龙宇 朱昕昀 +2 位作者 胡宇 韦祎 黄巍 《世界科学技术-中医药现代化》 CSCD 北大核心 2024年第5期1298-1307,共10页
目的基于脾虚大鼠模型探讨异功散中陈皮对人参皂苷类成分肠吸收变化的影响及其影响是否与P-gp蛋白外排作用有关。方法分组设计加入P-gp蛋白激动剂利福平与抑制剂维拉帕米,将36只SD大鼠随机分为空白对照组(6只)与模型组(30只),予以皮下... 目的基于脾虚大鼠模型探讨异功散中陈皮对人参皂苷类成分肠吸收变化的影响及其影响是否与P-gp蛋白外排作用有关。方法分组设计加入P-gp蛋白激动剂利福平与抑制剂维拉帕米,将36只SD大鼠随机分为空白对照组(6只)与模型组(30只),予以皮下注射利血平建立脾虚模型后将模型组分为异功散组(Y组)、去陈皮异功散组(Y-C组)、异功散利福平组(Y+R组)、去陈皮异功散利福平组(Y-C+R组)、去陈皮异功散维拉帕米组(Y-C+V组),以人参皂苷Rb1、人参皂苷Re及人参皂苷Rg1为指标成分,进行在体单向肠灌流实验,采用HPLC-MS测定指标成分含量并计算肠吸收动力学参数有效渗透系数(P_(eff))与吸收速率常数(K_(a))。结果与Y组相比,Y-C组中人参皂苷Rb1和人参皂苷Re在多个灌流时段的P_(eff)显著降低,Y+R组中人参皂苷Rb1、人参皂苷Re及人参皂苷Rg1的P_(eff)和K_(a)在多个灌流时段降低,表明陈皮促进人参皂苷Rb1和人参皂苷Re肠吸收且该作用与P-gp蛋白活性有关,但未能影响人参皂苷Rg1的肠吸收;与Y-C组相比,Y-C+V组中P-gp蛋白抑制剂维拉帕米使人参皂苷Rb1和人参皂苷Re在多个灌流时段P_(eff)显著升高,而Y-C+R组中P-gp蛋白激动剂利福平使人参皂苷Rb1、人参皂苷Re及人参皂苷Rg1的P_(eff)和K_(a)在多个灌流时段显著降低,说明无陈皮干预下,人参皂苷Rb1、人参皂苷Re及人参皂苷Rg1也可能是P-gp蛋白的底物。结论异功散中陈皮通过发挥抑制P-gp蛋白活性的类维拉帕米作用来促进人参皂苷Rb1和人参皂苷Re肠吸收。 展开更多
关键词 异功散 肠吸收动力学 在体单向肠灌流实验 P-gp蛋白
下载PDF
Li对Al-Zn-Mg-Cu系合金GP区转变动力学的影响 被引量:2
13
作者 魏芳 赵中魁 +3 位作者 周铁涛 刘培英 张永刚 陈昌麒 《中国有色金属学报》 EI CAS CSCD 北大核心 2003年第4期876-880,共5页
Al Zn Mg Cu系合金在较低温度时效时,形成2种类型的GP区:GP(Ⅰ)区和GP(Ⅱ)区。选用7075,7075+0.58%Li,7075+0.89%Li和7075+1.0%Li4种合金进行343K,240h和393K,24h时效,以获得GP区,并通过DSC实验结果,用Avrami Johnson Mehl(AJM)表达式... Al Zn Mg Cu系合金在较低温度时效时,形成2种类型的GP区:GP(Ⅰ)区和GP(Ⅱ)区。选用7075,7075+0.58%Li,7075+0.89%Li和7075+1.0%Li4种合金进行343K,240h和393K,24h时效,以获得GP区,并通过DSC实验结果,用Avrami Johnson Mehl(AJM)表达式计算了GP区溶解动力学参数,从而定量地研究Li对7075合金GP区转变的影响。结果表明:经过343K,240h时效后,含Li的7075合金的GP(Ⅰ)区溶解激活能较7075合金的略低,Li促进GP(Ⅰ)区的形成;经过393K,24h时效后,2种合金GP区溶解激活能相差不大。 展开更多
关键词 高强铝合金 gp DSC 组织转变动力学 时效
下载PDF
用差热法分析Al-Zn-Mg-Cu-Li合金组织转变动力学及TTT曲线 被引量:6
14
作者 魏芳 李金山 陈昌麒 《稀有金属材料与工程》 SCIE EI CAS CSCD 北大核心 2008年第8期1348-1351,共4页
采用差热法(DSC)对Al-Zn-Mg-Cu-Li合金在393K,24h和393K,3.5h+433K,12h时效过程中的组织转变动力学进行了分析,并用Avrami-Johnson-Mehl(AJM)表达式计算了GP区和η′相转变的动力学参数,进而得出了这两种组织转变的动力学表达式。根据TT... 采用差热法(DSC)对Al-Zn-Mg-Cu-Li合金在393K,24h和393K,3.5h+433K,12h时效过程中的组织转变动力学进行了分析,并用Avrami-Johnson-Mehl(AJM)表达式计算了GP区和η′相转变的动力学参数,进而得出了这两种组织转变的动力学表达式。根据TTT曲线的物理意义,对动力学表达式进行数学变形后得到了TTT曲线的数学表达式。通过该表达式计算的GP区和η′相转变的TTT动力学曲线与实验结果具有很好的一致性。 展开更多
关键词 Al-Zn-Mg-Cu-Li合金 gp η′相 动力学 TTT曲线
下载PDF
森林面积测量精度对比分析 被引量:12
15
作者 谭伟 张贤 王志杰 《山地农业生物学报》 2007年第6期495-498,共4页
通过在贵州山区(花溪区)不同林地条件下选设的多个点上进行面积测量试验,以全站仪测量结果为参考,对比分析实时动态GPS和罗盘仪在小班面积测量中的精度问题。研究表明,在进行森林资源调查小班面积测量时,其罗盘仪测量精度较GPS高;但是... 通过在贵州山区(花溪区)不同林地条件下选设的多个点上进行面积测量试验,以全站仪测量结果为参考,对比分析实时动态GPS和罗盘仪在小班面积测量中的精度问题。研究表明,在进行森林资源调查小班面积测量时,其罗盘仪测量精度较GPS高;但是随着面积增大,GPS面积测量相对误差减小,而罗盘仪测量误差相对呈增大的趋势,并且测量精度明显低于GPS测量。GPS在对有林地、灌木林地、疏林地进行面积测量时,受林分郁闭度影响较大,其精度随着林分郁闭度的增大而降低;而在草地和无林地中无明显影响。由于目前采用的GPS单机定位精度不够高,所以不能用单机进行林业用地小地块面积测量,宜用GPS差分定位技术测量。 展开更多
关键词 面积测量 精度 实时动态gps 罗盘仪 全站仪
下载PDF
利用Bernese5.0软件实现LEO卫星精密定轨 被引量:9
16
作者 汪楚 胡小工 郭鹏 《天文研究与技术》 CSCD 2011年第3期255-261,共7页
越来越多的LEO卫星装载了高精度的星载GPS接收机,星载GPS定轨已成为LEO卫星精密定轨的重要手段之一。星载GPS精密定轨精度依赖于GPS星历及钟差精度,采用CODE(Center for Orbit Determination in Europe)官方网站提供的GPS精密星历及钟... 越来越多的LEO卫星装载了高精度的星载GPS接收机,星载GPS定轨已成为LEO卫星精密定轨的重要手段之一。星载GPS精密定轨精度依赖于GPS星历及钟差精度,采用CODE(Center for Orbit Determination in Europe)官方网站提供的GPS精密星历及钟差数据,基于瑞士伯尼尔大学开发的Bernese 5.0软件,采用非差减缩动力学定轨方法,解算了60天的CHAMP卫星和SAC-C卫星轨道,并将所得轨道与JPL和GFZ事后科学轨道比较,得出的轨道位置三维精度优于20 cm量级,速度三维精度约为0.20 mm/s。 展开更多
关键词 精密定轨 星载gps 减缩动力学法 Bernese5.0软件
下载PDF
Structures of convection and turbulent kinetic energy in boundary layer over the southeastern edge of the Tibetan Plateau 被引量:6
17
作者 WANG YinJun XU XiangDe +3 位作者 ZHAO TianLiang SUN JiHua YAO WenQing ZHOU MingYu 《Science China Earth Sciences》 SCIE EI CAS CSCD 2015年第7期1198-1209,共12页
Based on a comprehensive analysis on Sonic Anemometer and gradient data, wind profile radar(WPR) and GPS sounding data of March–August 2008 from the boundary layer(BL) tower observation system at Dali on the southeas... Based on a comprehensive analysis on Sonic Anemometer and gradient data, wind profile radar(WPR) and GPS sounding data of March–August 2008 from the boundary layer(BL) tower observation system at Dali on the southeastern edge of Tibetan Plateau(TP), it is found that the strengths of turbulent kinetic energy(TKE), buoyancy term and shear term depend on vegetation cover in association with local stability and thermodynamic condition. Strong kinetic turbulence appears when near surface layer in neutral condition with the large contribution from shear term. In an unstable condition within near surface layer, the atmospheric turbulent motion is mainly thermal turbulence, as buoyancy term is obviously larger than shear term. Under a stable condition the intermittent turbulence is accompanied by weak shear and buoyancy term, and TKE is significantly less than neutral or instable condition. The study also presents that the buoyancy term contribution at Nyingchi station in the southern slopes of the TP large topography in spring is significantly larger than that at Dali over the southeastern TP edge, reflecting that the thermal turbulence makes an important contribution to convection activity in the southern slopes of TP. Dali station is located in complex terrain with mountain and valley leading to larger kinetic turbulence. From the perspective of interaction of turbulence-convection in different scales, the study revealed that the height of convective boundary layer(CBL) could reach up to 1500–2000 m. TKE, shear term, and buoyancy term in near surface layer have the notable correlations with BL height and local vertical motion. The daytime thermodynamic turbulence effect of heat flux and buoyancy term has an obvious impact on the height of CBL, whereas mechanical turbulence only exerts a less impact. Mechanical turbulence in near surface layer has a significant impact on vertical motion especially in the forenoon with impacting height of 2500–3000 m. The peaks in diurnal variations of shear term and buoyancy term correspond to the high instable periods, especially in summer forenoon. Our observation analysis characterized the convection activity triggered by TKE source and their interaction in the southeastern TP edge. 展开更多
关键词 gps sounding boundary layer height wind profile radar turbulent kinetic energy (TKE) TKE equation terms
原文传递
Kinetics of UV curable alkyl 3-mercaptopropionate-vinyl silizane
18
作者 Jiale SONG Lixin CHEN +2 位作者 Yazhou WANG Weiwei CHEN Rumin WANG 《Frontiers of Chemical Science and Engineering》 SCIE EI CSCD 2008年第4期390-395,共6页
Photopolymerization of vinyl-containing liquid silizane preceramic monomers copolymerized with thiol monomers,based on a step-growth radical polymerization mechanism,is a novel,rapid,inexpensive and simple tech-nique ... Photopolymerization of vinyl-containing liquid silizane preceramic monomers copolymerized with thiol monomers,based on a step-growth radical polymerization mechanism,is a novel,rapid,inexpensive and simple tech-nique for producing preceramic structures from liquid pre-cursors.The kinetics of alkyl 3-mercptopropionate-vinyl silizane under UV irradiation is investigated by using real-time Fourier transform infrarcd(FT-IR)and photo-dif-ferential scanning calorimetry(photo-DSC).The experi-mental results show preliminarily that:(1)about 80%conversion of vinyl group has been achieved in the pres-ence of a low concentration photoinitiator under UV irra-diation;(2)by increasing the functionalities of the thiol group,the peak rate of copolymerization increases and the final conversion of the vinyl group decreases;(3)the copolymerization is primarily a bimolecular radical ter-mination process;(4)the copolymerization is first-order,i.e.,its rate is proportional to the vinyl group concentra-tion and independent of the concentration of thiol group. 展开更多
关键词 UV copolymerization kineticS alkyl 3-mercap-topropionate vinyl silizane real-time FT-IR PHOTO-DSC
原文传递
Hierarchical under frequency load shedding scheme for inter-connected power systems 被引量:3
19
作者 Guowei Cai Shuyu Zhou +3 位作者 Cheng Liu Yuchi Zhang Shujia Guo Zhichong Cao 《Protection and Control of Modern Power Systems》 SCIE EI 2023年第2期292-303,共12页
Severe disturbances in a power network can cause the system frequency to exceed the safe operating range.As the last defensive line for system emergency control,under frequency load shedding(UFLS)is an important metho... Severe disturbances in a power network can cause the system frequency to exceed the safe operating range.As the last defensive line for system emergency control,under frequency load shedding(UFLS)is an important method for preventing a wide range of frequency excursions.This paper proposes a hierarchical UFLS scheme of“centralized real-time decision-making and decentralized real-time control”for inter-connected systems.The centralized decision-layer of the scheme takes into account the importance of the load based on the equivalent transformation of kinetic energy(KE)and potential energy(PE)in the transient energy function(TEF),while the load PE is used to determine the load shedding amount(LSA)allocation in different loads after faults in real-time.At the same time,the influence of inertia loss is considered in the calculation of unbalanced power,and the decentralized control center is used to implement the one-stage UFLS process to compensate for the unbalanced power.Simulations are carried out on the modified New England 10-generator 39-bus system and 197-bus system in China to verify the performance of the proposed scheme.The results show that,compared with other LSA allocation indicators,the proposed alloca-tion indicators can achieve better fnadir and td.At the same time,compared with other multi-stage UFLS schemes,the proposed scheme can obtain the maximum fnadir with a smaller LSA in scenarios with high renewable energy sources(RES)penetration. 展开更多
关键词 Hierarchical under frequency load shedding Centralized real-time decision-making and decentralized real-time control Transient energy function kinetic energy Potential energy
原文传递
汽车用新型Al-0.93Mg-0.78Si-0.20Cu-3.00Zn合金的制备及其时效析出行为研究 被引量:7
20
作者 李勇 郭明星 +4 位作者 姜宁 张许凯 张艳 庄林忠 张济山 《金属学报》 SCIE EI CAS CSCD 北大核心 2016年第2期191-201,共11页
通过DSC,OM,SEM,TEM观察及拉伸测试等手段对新开发的汽车用新型Al-0.93Mg-0.78Si-0.20Cu-0.30Mn-0.40Fe-3.00Zn(质量分数,%)合金的时效析出行为进行了系统研究.结果表明,固溶淬火态合金的DSC曲线出现5个放热峰,分别对应GP区聚集长大及... 通过DSC,OM,SEM,TEM观察及拉伸测试等手段对新开发的汽车用新型Al-0.93Mg-0.78Si-0.20Cu-0.30Mn-0.40Fe-3.00Zn(质量分数,%)合金的时效析出行为进行了系统研究.结果表明,固溶淬火态合金的DSC曲线出现5个放热峰,分别对应GP区聚集长大及沉淀相析出,运用Avrami-Johnson-Mehl方法对合金时效析出动力学进行了计算分析,创建的沉淀相析出动力学方程Y=1-exp[-2.03×10^(19)exp(-23573/T)t^2]可以比较准确地预测合金时效析出规律.185℃人工时效90 min即可达到峰值硬度133 HV,对应的拉伸性能可达σ_(0.2)=346 MPa,σ_b=383 MPa,δ=13%,拉伸断口仍以塑性断裂为主.虽然该合金含有一定量的Zn,但在185℃时效时仍以Mg-Si相的析出为主,峰时效态分布有结构稳定的b′′相及其前驱体pre-b′′相,后者的出现主要是由于Zn参与了沉淀相的析出所致.此外,根据合金时效过程的组织演化规律,提出了该新型合金沉淀相形核和析出模型示意图. 展开更多
关键词 Al-Mg-Si-Cu-Zn合金 gp b'相 pre-b'相 析出动力学
原文传递
上一页 1 2 下一页 到第
使用帮助 返回顶部