在一次数学竞赛中，某小组6名同学的成绩（单位：分）分别是69、75、86、92、95、88.这组数据的中位数是（　　）A. 79B. 86C. 92D. 87
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将这组数据按从小到大的顺序排列为：69，75，86，88，92，95，处于中间位置的那个数是86和88，那么由中位数的定义可知，这组数据的中位数是87．故选D．
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本题考查统计的有关知识，找中位数要把数据按从小到大的顺序排列，位于最中间的一个数或两个数的平均数为中位数．
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考点点评：
本题为统计题，考查中位数的意义．中位数是将一组数据从小到大（或从大到小）重新排列后，最中间的那个数（最中间两个数的平均数），叫做这组数据的中位数．如果中位数的概念掌握得不好，不把数据按要求重新排列，就会出错．
扫描下载二维码上传用户：zespnwnlbu资料价格：5财富值&&『』文档下载 ：『』&&『』学位专业：&关 键 词 ：&&&&&权力声明：若本站收录的文献无意侵犯了您的著作版权，请点击。摘要:（摘要内容经过系统自动伪原创处理以避免复制，下载原文正常，内容请直接查看目录。）固体氧化物燃料电池（SOFC）是将反响物的化学能直接转化为电能的电化学装配，其作为一种新型的，干净的动力，是处理动力应用率低和情况净化两重成绩的高新技巧。然则在SOFC历久运转中，发明其机能会产生急剧降低，寿命年夜年夜的下降，这是SOFC年夜规模的推行所面对的一个严重成绩，制约着SOFC的成长。进步SOFC机能的症结是取得可以或许抵抗老化和净化的高效力、长命命的电极。那末，若何优化微纳米多孔构造电极而使其具有抗腐化和净化才能是电池研讨和开辟的重点。无损取得电极外部连通孔隙和渠道等信息就显得很成心义，然则现有的试验办法（好比电镜）简直弗成能知足上述请求。为此，成长一种可以或许不雅察孔隙和渠道尺寸、散布和连通性的三维显微成像对象，原位无毁伤研讨SOFC电极三维构造及其在运作时的变更情形，对研讨这些具有纳米多孔构造的电极中物理和化学变更进程具有主要的意义。比来成长起来的基于波带片缩小成像的硬X射线三维成像技巧，因为具有强穿透性和地面间分辩率两年夜特征，并且无需机械切片，便可以获得较厚的庞杂资料的三维构造图象，而被普遍的运用于生物、医学、情况、资料和微电子等学科。合肥国度同步辐射试验室扶植了条基于波带片的硬X射线显微成像光束线站，其成像空间分辩率到达50纳米。基于此试验平台，本论文重要展开了以下几方面的任务：1。X射线显微成像试验站的调试和元素接收边成像试验办法的成长引见了国度同步辐射试验室（NSRL）的硬X射线显微成像体系，包含其重要光学元件、体系的特色及其机能。描写了NSRL成像站上的三种成像办法。在接收衬度成像的基本上成长了元素接收边成像办法。基于Ni一YSZ样品重点比拟了相位衬度成像和元素接收边成像的差别，展现了元素接收边成像的优胜性，为研讨物资的元素散布开拓了一个新的途径。2。 X射线元素接收边成像办法重构Ni一YSZ阳极的三维构造应用Ni的接收边特征重构出了Ni一YSZ阳极（包含功效层和支持层）的三维构造。基于获得三维重构片层胜利地把Ni一YSZ阳极中Ni、YSZ和Pore三相辨别开，成长了一系列的数据剖析办法来定量剖析Ni一YSZ阳极微构造，剖析了重构数据体积的靠得住性，在三维空间里提取到了阳极一些主要的构造参数，好比Ni、YSZ和Pore三相的体积分数、各相的连通性、各相均匀颗粒年夜小、各相的比外面面积和三相界面长度及散布，这些构造参数信息是没法用传统办法定量剖析盘算能获得的。Ni一YSZ阳极三维层面上的构造参数的获得为我们懂得其外部微不雅构造供给了需要的信息。3。基于元素接收边成像研讨了热轮回前提下Ni一YSZ功效层的微构造和机能演化为了懂得电极在应用进程中的退步机制，应用X射线元素接收边成像研讨了Ni一YSZ阳极功效层在热轮回前提下的构造演化，盘算并剖析了Ni、YSZ和Pore三相的一些参数变更。研讨注解热轮回进程中阳极资料中的Ni颗粒产生了集合景象，促使Ni颗粒变年夜。在低温情况下Ni颗粒的迁徙招致Ni相的连通性变的比拟差，连通的Ni变少导致其导电才能变弱，详细表示为阳极的电导率会变小，对样品停止的电化学测试成果证明了这一点。另外，跟着阳极热轮回次数增长，其外部总的和连通的三相界面（TPB）长度值都是逐步的变小，这就解释在热轮回前提下，阳极内的反响位点在逐步的削减，进而会影响其外部的氧离子复原反响速度，下降电极的机能，终究招致电池的整体机能变差。4。燃料电池阴极的三维构造表征研讨LSM一YSZ阴极的孔隙是一个比拟主要的构造参数，但是因为阴极自己的厚度很薄，很难去应用传统的测孔隙率办法测得阴极中的孔隙率年夜小。本任务应用相位衬度成像办法胜利重构了LSM一YSZ阴极功效层的三维构造。基于重构获得的三维数据，定量盘算了LSM一YSZ阴极的孔隙率、连通孔隙率和歪曲因子等构造参数。基于对LSM一YSZ阴极三维构造的胜利表征，进一步地研讨了分歧烧结时光下阴极三维微构造的演化。定量盘算了分歧烧结时光下阴极的一些症结参数，发明孔隙率跟着烧结时光的增长而降低；孔隙与LSM一YSZ颗粒的均匀直径和孔隙的歪曲因子会跟着烧结时光的延伸而增年夜。这为研讨陶瓷的烧结机理供给了直不雅的试验数据，也为优化阴极的制备前提供给了信息。应用Fe的K接收边成像研讨了LaSrFeO一YSZ阴极的纳米三维构造。胜利地朋分出LaSrFeO、YSZ和Pore这三相，盘算个中的一些症结参数，好比各相体积分数、各项连通性和三相界面长度等。偏重点评论辩论了重构体体积年夜小对三相体积分数的影响。Abstract:Solid oxide fuel cell (SOFC) is the response of direct conversion of chemical energy into electrical energy of electrochemical assembly as a new, clean energy is processing power application rate is low and the purification double achievement of new and high technology. However in SOFC to long-term operation, the invention of the function will have drastically reduced, life greatly decreased, which is the implementation of the scale of the eve of the SOFC faces a serious problem, which restricts the growth of SOFC. The progress of SOFC function is the crux of the electrode can be resistant to aging and purification of high efficiency and long life. Then, how to optimize the structure of micro nano porous electrode which has anti corruption and purification ability is the research and development of the key battery. Nondestructive external electrodes connected pores and channels and other information is very meaningful. However the existing test methods (like electron microscopy) almost impossible to satisfy the request. Therefore, grow a may not Yacha pores and channels size, distribution and connectivity can be of microscopy 3D imaging object, in situ without damage research of SOFC electrodes three-dimensional structure and in operation when the changes, to discuss these with nano porous structure of the electrode in the physical and chemical change process is of major significance. Grew up in the ratio based on Fresnel zone plate (FZP) to narrow the imaging of the hard X-ray 3D imaging techniques, because has strong penetration and the ground resolution two of the eve of the features, and without the need for mechanical sectioning, thick complex data of the 3D structure of image, and is widely used in biology, medicine, information, material and microelectronics discipline. Hefei National Synchrotron Radiation Laboratory builds a station based on Fresnel zone plate hard X ray imaging beamline, the imaging resolution rate reached 50 nm. This test platform based on this paper carried out the following tasks: 1. Debugging and elements of X-ray imaging and microscope test station receives the growth of side imaging test method introduces the National Synchrotron Radiation Laboratory (NSRL) of hard X ray imaging system, contains the important optical components, system characteristic and its function. Describes the three kinds of imaging methods on NSRL imaging. In the receiving contrast imaging basically grow up elements of receiving and imaging measures. Ni is a sample of the YSZ key comparison of phase contrast imaging and imaging based on the difference of the receiving side elements, show the superiority of receiving side imaging elements, as the research material element spread has opened up a new way. 2. The receiving element receives the X ray imaging method Ni YSZ edge reconstruction of the 3-D structure of anode using Ni edge feature reconstruct Ni YSZ anode (including function layer and support layer of the 3D structure). Based on 3D reconstruction slice victory the Ni YSZ anode Ni and YSZ and pore phase discrimination open, grow a series of data analysis method to quantitative analysis of Ni YSZ anode micro structure, and analyzes the reliability of the reconstructed volume, in the three-dimensional space to extract the anode some important structural parameters, like the volume fraction of Ni and YSZ and pore phase, the phase of connectivity, uniform phase particles of the eve of the small, each phase than outside area and three-phase boundary length and spread, these structural parameter information is can not use traditional methods of quantitative analysis and calculation to obtain. To obtain a three-dimensional structure parameter Ni YSZ anode on the level of the us to understand the external micro structure provides the information necessary. 3. Based on element to receive side imaging research the thermal cycle under the premise of the efficacy of Ni YSZ layer micro structure and function of evolution in order to understand electrode in the application process in the degeneration of mechanism, application of X-ray element receiving side imaging study the Ni YSZ anode functional layer in thermal cycling under the premise of tectonic evolution. Calculation and analysis of the change of some parameters of the Ni and YSZ and pore phase. Research shows the Ni particles in the process of thermal cycle data set generated in the anode scene, make Ni particles become large. Under the low temperature Ni particle migration lead to Ni phase connectivity of the relatively poor, variable connectivity of Ni leads to less the conductive to become weak, detailed representation for anode conductivity becomes smaller, on samples of the electrochemical test results prove that this. In addition, along with the anode heat cycle number increases, the external general and connected three-phase boundary (TPB) length values are gradually become smaller, which may explain under thermal cycling conditions, anode reaction sites in the gradual reduction and effect of the external oxygen ion recovery response speed, electrode decreased function, eventually lead to battery overall performance variation. 4. The pores of the fuel cell cathode three-dimensional structural characterization studies LSM YSZ cathode is a match the main structure parameters, but because the cathode thickness is thin, it is difficult to application of the traditional measuring method of porosity measured porosity of the eve of the cathode with small. The task of application of phase contrast imaging method to reconstruct the 3D structure of a LSM victory YSZ cathode layer effect. The 3D data reconstruction based on quantitative calculation LSM YSZ cathode porosity, porosity and distortion factor connected structure parameters. The victory of a characterization of LSM YSZ cathode based on three-dimensional structure, further study the evolution of the sintering time differences under the cathode three-dimensional micro structure. Quantitative calculation of the cathode under different sintering time some sticking parameter, the invention porosity followed sintering time
pore and LSM YSZ particles of uniform pore diameter and the warp factor will be along with the extension of the sintering time increases. This provides experimental data intuitive for ceramic sintering mechanism research, but also for the optimization of cathode preparation before providing information. The application of Fe K imaging on the receiving side of a three-dimensional structure of LaSrFeO nano YSZ cathode. Win friends out the LaSrFeO, YSZ and Pore three phase, some parameters calculating the crux, like all the fractions, the connectivity and three-phase boundary length etc.. Emphasis discusses influence the reconstruction volume size of phase volume fraction.目录:摘要5-7Abstract7-9目录10-13第1章 绪论13-39&&&&1.1 引言13-14&&&&1.2 燃料电池简介14-15&&&&1.3 固体氧化物燃料电池15-22&&&&&&&&1.3.1 SOFC的工作原理及特点15-16&&&&&&&&1.3.2 固体氧化物燃料电池部件16-21&&&&&&&&1.3.3 燃料电池性能退化问题21-22&&&&1.4 电池电极微结构的成像方法22-36&&&&&&&&1.4.1 光学显微镜方法22-24&&&&&&&&1.4.2 扫描电子显微镜(SEM)技术24-27&&&&&&&&1.4.3 聚焦离子束电子束扫描电镜(FIB-SEM)技术27-30&&&&&&&&1.4.4 高空间分辨X射线显微成像技术30-36&&&&1.5 论文主要工作和内容安排36-39第2章 高分辨元素吸收边成像方法及应用39-53&&&&2.1 高分辨X射线显微成像实验站简介39-42&&&&&&&&2.1.1 同步辐射光源光源和硬X射线光束线39-40&&&&&&&&2.1.2 X射线显微成像装置40-42&&&&2.2 NSRLX射线显微成像的三种成像模式42-48&&&&&&&&2.2.1 吸收衬度成像42-43&&&&&&&&2.2.2 泽尼克相位衬度成像43-44&&&&&&&&2.2.3 元素吸收边成像44-48&&&&2.3 NSRL三种成像模式结果比较48-51&&&&&&&&2.3.1 吸收衬度和相位衬度成像对比49&&&&&&&&2.3.2 相位衬度成像和元素吸收边成像对比49-51&&&&2.4 本章小结51-53第3章 显微成像研究固体燃料电池阳极微结构53-74&&&&3.1 NI-YSZ阳极的准备53-54&&&&&&&&3.1.1 Ni-YSZ的制备53-54&&&&&&&&3.1.2 用于X射线成像的Ni-YSZ阳极样品准备54&&&&3.2 NI-YSZ支撑层的X射线显微成像54-68&&&&&&&&3.2.1 Ni-YSZ的X射线成像实验54-57&&&&&&&&3.2.2 三维重构数据分割和渲染57-60&&&&&&&&3.2.3 Ni-YSZ阳极支撑层三维重构数据分析60-68&&&&3.3 NI-YSZ功能层的显微成像研究68-73&&&&&&&&3.3.1 Ni-YSZ功能层样品成像69&&&&&&&&3.3.2 Ni-YSZ功能层重构数据分析69-73&&&&3.4 本章小结73-74第4章 热循环下的阳极微结构及其电性能成像研究74-83&&&&4.1 研究背景74&&&&4.2 样品准备74-75&&&&4.3 实验75-77&&&&&&&&4.3.1 X射线成像样品制备75&&&&&&&&4.3.2 X射线成像实验75-76&&&&&&&&4.3.3 四端子法测电导率76-77&&&&4.4 数据分析和讨论77-82&&&&&&&&4.4.1 平均Ni和YSZ颗粒大小的计算77-78&&&&&&&&4.4.2 Ni和YSZ相的表面积计算78-79&&&&&&&&4.4.3 单位体积三相界面长度计算79-80&&&&&&&&4.4.4 Ni和YSZ连通性的计算80-81&&&&&&&&4.4.5 样品电导率测量81-82&&&&4.5 本章小结82-83第5章 燃料电池阴极的微结构显微成像研究83-105&&&&5.1 (LA_(0.8)SR_(0.2))_(0.95)MNO_3-YSZ显微成像研究83-89&&&&&&&&5.1.1 研究背景83-84&&&&&&&&5.1.2 LSM-YSZ功能层样品制备84-85&&&&&&&&5.1.3 LSM-YSZ功能层成像实验85-87&&&&&&&&5.1.4 孔隙率计算及可靠性研究分析87&&&&&&&&5.1.5 孔隙率连通性计算87-88&&&&&&&&5.1.6 孔隙扭曲因子计算88-89&&&&5.2 不同烧结时间的LSM-YSZ功能层的三维结构研究89-95&&&&&&&&5.2.1 研究背景89-90&&&&&&&&5.2.2 不同烧结时间LSM-YSZ样品的制备90-91&&&&&&&&5.2.3 不同烧结时间LSM-YSZ成像实验91-92&&&&&&&&5.2.4 不同烧结时间LSM-YSZ孔隙率计算92-93&&&&&&&&5.2.5 不同烧结时间LSM-YSZ中孔隙扭曲因子计算93-94&&&&&&&&5.2.6 LSM-YSZ中颗粒与孔径的平均直径和表面积计算94-95&&&&5.3 LASRFEOO-YSZ阴极结构三维成像研究95-103&&&&&&&&5.3.1 LaSrFeO-YSZ阴极样品的制备95-96&&&&&&&&5.3.2 LaSrFeO-YSZ样品的三维成像实验96-98&&&&&&&&5.3.3 LaSrFeO-YSZ的体积可靠性分析98-103&&&&&&&&5.3.4 各相连通性和TPB长度的分析103&&&&5.4 本章小结103-105第6章 总结与展望105-107参考文献107-117致谢117-119在读期间发表的学术论文与取得的研究成果119-120分享到：相关文献|在一次数学竞赛中，某小组6名同学的成绩（单位：分）分别是69、75、86、92、95、88．这组数据的中位数是_百度知道
在一次数学竞赛中，某小组6名同学的成绩（单位：分）分别是69、75、86、92、95、88．这组数据的中位数是
在一次数学竞赛中、92、75、86：分）分别是69，某小组6名同学的成绩（单位、95
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分析，那么由中位数的定义可知：本题考查统计的有关知识，88，92，位于最中间的一个数或两个数的平均数为中位数．将这组数据按从小到大的顺序排列为，处于中间位置的那个数是86和88，找中位数要把数据按从小到大的顺序排列，95，86
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出门在外也不愁在一次数学竞赛中，某小组6名同学的成绩（单位：分）分别是69、75、86、92、95、88，这组数据的中位数是
A.79 B.86 C.92 D.87
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