在读英文文献时,我们难免遇到缩写的数学英文符号,对第一次接触此类符号的学者造成了一定的困扰,这里笔者列出自己碰到的一些常用的符号,希望对大家也有所帮助。 1. w.r.t. ------- with respect to 常用于求导,或者满足一定条件之类的情况 2. s.t. ------- subject to 约束与 3. r.v. ------- random variable 随机变量 4. iff ------- if and only if 5. i.i.d. ------- independently and identically distributed 独立同分布 持续更新中。。。
什么是曼-惠特尼U检验 曼-惠特尼U检验 又称“ 曼-惠特尼秩和检验 ”,是由 H.B.Mann 和 D.R.Whitney 于1947年提出的。它假设两个样本分别来自除了总体均值以外完全相同的两个总体,目的是检验这两个总体的均值是否有显著的差别。 曼-惠特尼秩和检验可以看作是对两均值之差的参数检验方式的 T检验 或相应的大样本正态检验的代用品。由于曼-惠特尼秩和检验明确地考虑了每一个样本中各测定值所排的秩,它比 符号检验法 使用了更多的信息。 曼-惠特尼U检验的步骤 Computation of the U test begins by arbitrarily designating two samples as group 1 and group 2.the data from the two groups are combined into one group ,with each data value retaining a group identifier of its original group.the pooled values are then ranked from 1 to n,with the smallest value being assigned a rank of 1. The sum of the ranks of Values from group 1 is computed and designated as W1 and the sum of the ranks of values from group 2 is designated as W2 . 该方法的具体步骤如下: 第一步: 将两组数据混合,并按照大小顺序编排等级。最小的数据等级为1,第二小的数据等级为2,以此类推(若有数据相等的情形,则取这几个数据排序的平均值作为其等级)。 第二步: 分别求出两个样本的等级和 W 1 、 W 2 。 第三步: 计算曼-惠特尼U检验统计量, n 1 为第一个样本的量, n 2 为第二个样本的量: 选择 U 1 和 U 2 中最小者与临界值 U α 比较,当 U U A 时,拒绝 H 0 ,接受 H 1 。 在原假设为真的情况下, 随机变量 U的均值和 方差 分别为: 当 n 1 和 n 2 都不小于10时,随机变量近似服从正态分布。 第四步: 作出判断。 设第一个总体的均值为 μ 1 ,第二个总体的均值为 μ 2 ,则有: 1) ,如果 Z − Z α ,则拒绝 H 0 ; 2) ,如果 Z Z α ,则拒绝 H 0 ; 3) ,如果 Z − Z a l p h a / 2 ,则拒绝 H 0 。 曼-惠特尼U检验的应用举例 下面是两种不同加工方式的菜粕在黄牛瘤胃内培养16h的干物质降解率,用曼-惠特尼U检验比较其有无差异: 两种加工方式的菜粕瘤胃培养16h的干物质降解率(%) 预压浸出组 等级排序 螺旋热榨组 等级排序 39.33 3 42.91 5 44.10 8 44.69 10 35.89 1 44.54 9 43.35 6 45.31 11 47.61 13 37.73 2 43.71 7 48.75 14 46.71 12 41.85 4 先按照大小顺序排列等级(见上表),而后计算 W 1 = 38, W 2 = 67, n 1 = 6, n 2 = 8 。 假设两种菜粕的16h瘤胃干物质降解率除了平均水平以外在其它方面无差异,即检验: H 0 :两种菜粕的16h瘤胃干物质降解率无差异; H 1 :两种菜粕的16h瘤胃干物质降解率有差异。 计算U值: U 2 值较小,选取 U 2 与 U α (α=0.05)比较,通过查表(附表)可知 U α = 8, U 2 U α ,即接受 H 0 ,认为两种加工方式的菜粕瘤胃培养16h的干物质降解率无显著差异。 附表: 曼-惠特尼检验U的临界值表 (仅列出单侧检验在0.025或双侧检验在0.05处的U临界值) n 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 n 1 1 2 0 0 0 0 1 1 1 1 3 0 1 1 2 2 3 3 4 4 5 5 4 0 1 2 3 4 4 5 6 7 8 9 10 5 0 1 2 3 5 6 7 8 9 11 12 13 14 6 1 2 3 5 6 8 10 11 13 14 16 17 19 7 1 3 5 6 8 10 12 14 16 18 20 22 24 8 0 2 4 6 8 10 13 15 17 19 22 24 26 29 9 0 2 4 7 10 12 15 17 20 23 26 28 31 34 10 0 3 5 8 11 14 17 20 23 26 29 33 36 39 11 0 3 6 9 13 16 19 23 26 30 33 37 40 44 12 1 4 7 11 14 18 22 26 29 33 37 41 45 49 13 1 4 8 12 16 20 24 28 33 37 41 45 50 54 14 1 5 9 13 17 22 26 31 36 40 45 50 55 59 15 1 5 10 14 19 24 29 34 39 44 49 54 59 64
答网友晶体学问题:单斜晶系的空间群符号 问题在: http://blog.sciencenet.cn/home.php?mod=spaceuid=2321do=wall 回答如下: 根据你提供的信息( ICSD #33243 :单斜钒酸铋 )。 ICSD 33243 数据(摘要)如下: Structured Bi (V O4) Unit Cell 5.197 5.096 11.702 90. 90. 90.4 Space Group I 1 1 2/b SG Number 15 Atom # OX SITE x y z SOF Bi 1 +3 4 e 0 0.25 0.6337(1) 1. V 1 +5 4 e 0 0.25 0.1352(5) 1. O 1 -2 8 f 0.149(3) 0.506(8) 0.210(2) 1. O 2 -2 8 f 0.258(3) 0.379(8) 0.451(2) 1. *end for ICSD #33243 在国际空间群表里, 15 号空间群有 6 种表达方式: Uniq-b 轴有三种晶胞, Uniq-c 轴有三种晶胞,共有 6 种。 注意, 6 种晶胞对应一个空间群编号,但是 6 种晶胞的 Patterson symmetry 符号不同。例如,你的数据( ICSD #33243 )对应 I 1 1 2/b , 根据这个符号确定空间群表里的具体晶胞选择。根据 Unit Cell 的( 5.197 5.096 11.702 90. 90. 90.4 ) 信息,可以确定属于 Uniq-c 轴,对应的晶胞如下: 注意,原子坐标的数据是和晶胞数据对应的。 BiVO4 的原子环境数据如下: a=,5.197,b=,5.096,c=,11.702,Delta=,.005 1 4e-Bi, is a reference atom Cartesian = ,-2.5896,-1.274,1.5681 SP coordinates=,0,.25,.634 ,1,1,The shell structure as a cluster:,shell,No,1 d of neighbors from the reference atom =,2.3434 The number of neighbor atoms, N=,2,and the number of shortest bonds formed by these atoms=,1 and the shortest bond length=,2.94 Neighbor atom:,8f-1-O Cartesian = ,-3.3726,-.0306,3.3936 SP coordinates= ,-.149,.494,.79 Neighbor atom:,8f-1-O Cartesian = ,-1.8066,-2.5174,3.3936 SP coordinates= ,.149,.006,.79 ,1,2,The shell structure as a cluster:,shell,No,2 d of neighbors from the reference atom =,2.3734 The number of neighbor atoms, N=,2,and the number of shortest bonds formed by these atoms=,1 and the shortest bond length=,4.4 Neighbor atom:,8f-1-O Cartesian = ,-4.4051,-2.5174,2.4574 SP coordinates= ,-.351,.006,.71 Neighbor atom:,8f-1-O Cartesian = ,-.7741,-.0306,2.4574 SP coordinates= ,.351,.494,.71 ,1,3,The shell structure as a cluster:,shell,No,3 d of neighbors from the reference atom =,2.5292 The number of neighbor atoms, N=,2,and the number of shortest bonds formed by these atoms=,1 and the shortest bond length=,4.65 Neighbor atom:,8f-2-O Cartesian = ,-3.9436,.6166,.5734 SP coordinates= ,-.258,.621,.549 Neighbor atom:,8f-2-O Cartesian = ,-1.2356,-3.1645,.5734 SP coordinates= ,.258,-.121,.549 ,1,4,The shell structure as a cluster:,shell,No,4 d of neighbors from the reference atom =,2.6084 The number of neighbor atoms, N=,2,and the number of shortest bonds formed by these atoms=,1 and the shortest bond length=,2.98 Neighbor atom:,8f-2-O Cartesian = ,-3.9258,-1.9313,-.5734 SP coordinates= ,-.258,.121,.451 Neighbor atom:,8f-2-O Cartesian = ,-1.2534,-.6166,-.5734 SP coordinates= ,.258,.379,.451 ,1,5,The shell structure as a cluster:,shell,No,5 d of neighbors from the reference atom =,3.6058 The number of neighbor atoms, N=,2,and the number of shortest bonds formed by these atoms=,1 and the shortest bond length=,6.93 Neighbor atom:,8f-2-O Cartesian = ,-3.9081,-4.4793,.5734 SP coordinates= ,-.258,-.379,.549 Neighbor atom:,8f-2-O Cartesian = ,-1.2712,1.9313,.5734 SP coordinates= ,.258,.879,.549 ,1,6,The shell structure as a cluster:,shell,No,6 d of neighbors from the reference atom =,3.6266 The number of neighbor atoms, N=,2,and the number of shortest bonds formed by these atoms=,1 and the shortest bond length=,7.25 Neighbor atom:,4e-V Cartesian = ,-5.1703,-3.8219,1.5798 SP coordinates= ,-.5,-.25,.635 Neighbor atom:,4e-V Cartesian = ,-.0089,1.274,1.5798 SP coordinates= ,.5,.75,.635 2 4e-V, is a reference atom Cartesian = ,-2.5896,-1.274,-4.2712 SP coordinates=,0,.25,.135 ,2,1,The shell structure as a cluster:,shell,No,1 d of neighbors from the reference atom =,1.7431 The number of neighbor atoms, N=,2,and the number of shortest bonds formed by these atoms=,1 and the shortest bond length=,2.85 Neighbor atom:,8f-2-O Cartesian = ,-3.8519,-.6166,-5.2776 SP coordinates= ,-.242,.379,.049 Neighbor atom:,8f-2-O Cartesian = ,-1.3273,-1.9313,-5.2776 SP coordinates= ,.242,.121,.049 ,2,2,The shell structure as a cluster:,shell,No,2 d of neighbors from the reference atom =,1.7486 The number of neighbor atoms, N=,2,and the number of shortest bonds formed by these atoms=,1 and the shortest bond length=,3.02 Neighbor atom:,8f-1-O Cartesian = ,-3.3549,-2.5785,-3.3936 SP coordinates= ,-.149,-.006,.21 Neighbor atom:,8f-1-O Cartesian = ,-1.8244,.0306,-3.3936 SP coordinates= ,.149,.506,.21 ,2,3,The shell structure as a cluster:,shell,No,3 d of neighbors from the reference atom =,2.89 The number of neighbor atoms, N=,2,and the number of shortest bonds formed by these atoms=,1 and the shortest bond length=,4.5 Neighbor atom:,8f-1-O Cartesian = ,-4.4229,.0306,-2.4574 SP coordinates= ,-.351,.506,.29 Neighbor atom:,8f-1-O Cartesian = ,-.7564,-2.5785,-2.4574 SP coordinates= ,.351,-.006,.29 ,2,4,The shell structure as a cluster:,shell,No,4 d of neighbors from the reference atom =,3.1239 The number of neighbor atoms, N=,2,and the number of shortest bonds formed by these atoms=,1 and the shortest bond length=,4.53 Neighbor atom:,8f-2-O Cartesian = ,-3.8341,-3.1645,-6.4244 SP coordinates= ,-.242,-.121,-.049 Neighbor atom:,8f-2-O Cartesian = ,-1.3451,.6166,-6.4244 SP coordinates= ,.242,.621,-.049 ,2,5,The shell structure as a cluster:,shell,No,5 d of neighbors from the reference atom =,3.6266 The number of neighbor atoms, N=,2,and the number of shortest bonds formed by these atoms=,1 and the shortest bond length=,7.25 Neighbor atom:,4e-Bi Cartesian = ,-5.1703,-3.8219,-4.2829 SP coordinates= ,-.5,-.25,.134 Neighbor atom:,4e-Bi Cartesian = ,-.0089,1.274,-4.2829 SP coordinates= ,.5,.75,.134 ,2,6,The shell structure as a cluster:,shell,No,6 d of neighbors from the reference atom =,3.652 The number of neighbor atoms, N=,2,and the number of shortest bonds formed by these atoms=,1 and the shortest bond length=,7.3 Neighbor atom:,4e-Bi Cartesian = ,-5.2059,1.274,-4.2829 SP coordinates= ,-.5,.75,.134 Neighbor atom:,4e-Bi Cartesian = ,.0267,-3.8219,-4.2829 SP coordinates= ,.5,-.25,.134 3 8f-1-O, is a reference atom Cartesian = ,-1.8066,-2.5174,3.3936 SP coordinates=,.149,.006,.79 ,3,1,The shell structure as a cluster:,shell,No,1 d of neighbors from the reference atom =,1.7486 The number of neighbor atoms, N=,1,and the number of shortest bonds formed by these atoms=,0 and the shortest bond length=,0 Neighbor atom:,4e-V Cartesian = ,-2.5718,-3.8219,4.2712 SP coordinates= ,0,-.25,.865 ,3,2,The shell structure as a cluster:,shell,No,2 d of neighbors from the reference atom =,2.3434 The number of neighbor atoms, N=,1,and the number of shortest bonds formed by these atoms=,0 and the shortest bond length=,0 Neighbor atom:,4e-Bi Cartesian = ,-2.5896,-1.274,1.5681 SP coordinates= ,0,.25,.634 ,3,3,The shell structure as a cluster:,shell,No,3 d of neighbors from the reference atom =,2.3734 The number of neighbor atoms, N=,1,and the number of shortest bonds formed by these atoms=,0 and the shortest bond length=,0 Neighbor atom:,4e-Bi Cartesian = ,.0089,-1.274,4.2829 SP coordinates= ,.5,.25,.866 4 8f-2-O, is a reference atom Cartesian = ,-1.3273,-1.9313,-5.2776 SP coordinates=,.242,.121,.049 ,4,1,The shell structure as a cluster:,shell,No,1 d of neighbors from the reference atom =,1.7431 The number of neighbor atoms, N=,1,and the number of shortest bonds formed by these atoms=,0 and the shortest bond length=,0 Neighbor atom:,4e-V Cartesian = ,-2.5896,-1.274,-4.2712 SP coordinates= ,0,.25,.135 ,4,2,The shell structure as a cluster:,shell,No,2 d of neighbors from the reference atom =,2.5293 The number of neighbor atoms, N=,1,and the number of shortest bonds formed by these atoms=,0 and the shortest bond length=,0 Neighbor atom:,4e-Bi Cartesian = ,.0267,-3.8219,-4.2829 SP coordinates= ,.5,-.25,.134 ,4,3,The shell structure as a cluster:,shell,No,3 d of neighbors from the reference atom =,2.6084 The number of neighbor atoms, N=,1,and the number of shortest bonds formed by these atoms=,0 and the shortest bond length=,0 Neighbor atom:,4e-Bi Cartesian = ,.0089,-1.274,-7.4191 SP coordinates= ,.5,.25,-.134 更多的数据可下载: BiVO4-15-Mono-Uniq-c-AEC-1-原子输出- .005.rar BiVO4-15-Mono-Uniq-c-AEC-1-配位数-简化版-修改- .005.rar
今天写论文时,想输入一个卡方的符号,以前都是粘贴老师给的,后来被我丢了,自己摸索了半天,似乎不是X,后来网上找到些资料,但只学会了粘贴, 还是不会在word里直接输,求各位看过本文的老师解答,特此感谢! 网上的资料: 特殊的统计学符号: 一、复制粘贴法。 很多难写的统计学符号其实都是一些小图片, 将所用符号直接从其他论文中复制粘贴至自己文章中即可,如果大小不合适,可以适当双击等比例调整图片大小即可。 算术平均数(用英文小写斜体)? 标准差(用英文小写斜体) s 标准误(用英文小写斜体)? t 检验(用英文小写斜体) t F 检验(用英文大写斜体) F 卡方检验(用希文大写斜体) χ2 相关系数(用英文小写斜体) r 概率(用英文大写斜体) P 样本数用英文斜体 n 总体均数 μ 标准误符号 总体均数的可信区间(CI)范围 二、采用公式编辑器。 这个不会 一般微软office自带有公式编辑器,通过点击“插入”--“对象”--Microsoft公式3.0即可调入打开。大家也可到网络中下载,体积很小,不占容量。? 参考地址: http://yufanghome.blog.hexun.com/25094433_d.html
稀土是一种极其重要的战略资源。我国的稀土矿藏世界第一。 近日,据浙江省地质矿产厅消息和本地重要媒体《钱江晚报》报道,浙西北或有一个大型的稀土钪矿藏!含钪70吨,价值至少700亿元,单价比黄金还贵四倍! 钪的化学符号是Sc, 原子序数 21,是一种柔软、银白色的过渡金属。在地壳中的平均丰度很低, 相当于每一吨地壳物质里面有5克(一小块德芙巧克力或者大白兔奶糖) ,而且分布极为分散,是典型的稀散亲石元素。钪的化学活性很高,很难制得高纯度金属,虽然1879年就被发现,但直到1973年才制得纯度为99.9%的金属钪。钪的优异性能仍使其在电光源、宇航、电子工业、核技术、超导技术等重要领域获得重要应用。 参考资料: (1) http://www.chinaccm.com/14/1403/140301/news/20001120/114309.asp (2) http://baike.baidu.com/view/26312.htm (3) http://finance.eastmoney.com/news/1350,20110331127664797.html Parts of the MiG-29 are made from Al-Sc alloy.