dft时域循环卷积与dtft，dfs时域卷积有何联系与区别
当有限长序列x(n)和h(n)的长度分别为N1和N2，取N>=max(N1,N2)，当N>=N1+N2-1，则线性卷积与圆周卷积相同。线性卷积是在时域描述线性系统输入和输出之间关系的一种运算。这种运算在线性系统分析和信号处理中应用很多，通常简称卷积。两个函数的圆周卷积是由他们的周期延伸所来定义的。周期延伸意思是把原本的函数平移某个周期T的整数倍后再全部加起来所产生的新函数。离散信号的圆周卷积可以经由圆周卷积定理使用快速傅立叶变换（FFT）而有效率的计算。因此，若原本的（线性）卷积能转换成圆周卷积来计算，会远比直接计算更快速。考虑到长度L和长度M的有限长度离散信号，做卷积之后会成为长度L＋M－1的信号，因此只要把两离散信号补上适当数目的零（zero-padding）成为N点信号，其中N≥L＋M－1，则它们的圆周卷积就与卷积相等。即可接着用N点FFT作计算。
数字信号处理 DFT DTFT DFS之间什么区别啊？谢谢。。。
1、定义不同： DTFT是离散时间傅里叶变换 ，它用于离散非周期序列分析；DFT只是对一周期内的有限个离散频率的表示；DFS是周期序列的离散傅里叶级数。2、DFS是对离散周期信号进行级数展开，DFS是DFT的周期延拓；DFT是将DFS取主值，3、 DTFT是是对序列的FT，得到连续的周期谱，而DFT得到是有限长的非周期离散谱。扩展资料：1、DFT：离散傅里叶变换（Discrete Fourier Transform，缩写为DFT），是傅里叶变换在时域和频域上都呈离散的形式，将信号的时域采样变换为其DTFT的频域采样。在形式上，变换两端（时域和频域上）的序列是有限长的，而实际上这两组序列都应当被认为是离散周期信号的主值序列。即使对有限长的离散信号作DFT，也应当将其看作其周期延拓的变换。2、DTFT，离散时间傅里叶变换（DTFT，Discrete-time Fourier Transform），是傅里叶变换的一种。也可以叫做序列的傅里叶变换。3、DFS也即离散傅里叶级数，又称离散时间傅里叶级数即DTFS，T代表时间。和连续周期信号相比，离散周期信号的离散傅里叶级数的频谱是周期性的，因为时域的连续对应于频率的非周期，时域的离散对应于频率的周期。
何时使用hadoop fs，hadoop dfs与hdfs dfs命令
hadoop fs：使用面广操作任何文件系统
hadoop dfs与hdfs dfs：能操作HDFS文件系统相关（包括与Local FS间操作）前者已经Deprecated般使用者
Following are the three commands which appears same but have minute differences
hadoop fs {args}
hadoop dfs {args}
hdfs dfs {args}
hadoop fs
FS
relates to a generic file system which can point to any file systems
like local, HDFS etc. So this can be used when you are dealing with
different file systems such as Local FS, HFTP FS, S3 FS, and others
hadoop dfs
dfs
is very specific to HDFS. would work for operation relates to HDFS.
This has been deprecated and we should use hdfs dfs instead.
hdfs dfs
same as 2nd i.e would work for all the operations related to HDFS and is the recommended command instead of hadoop dfs
below is the list categorized as HDFS commands.
**#hdfs commands**
namenode|secondarynamenode|datanode|dfs|dfsadmin|fsck|balancer|fetchdt|oiv|dfsgroups
So even if you use Hadoop dfs , it will look locate hdfs and delegate that command to hdfs dfs
何时使用hadoop fs，hadoop dfs与hdfs dfs命令
hadoop fs：使用面广操作任何文件系统hadoop dfs与hdfs dfs：能操作HDFS文件系统相关（包括与Local FS间操作）前者已经Deprecated般使用者Following are the three commands which appears same but have minute differenceshadoop fs {args}hadoop dfs {args}hdfs dfs {args}hadoop fs FS relates to a generic file system which can point to any file systems like local, HDFS etc. So this can be used when you are dealing with different file systems such as Local FS, HFTP FS, S3 FS, and others hadoop dfs dfs is very specific to HDFS. would work for operation relates to HDFS. This has been deprecated and we should use hdfs dfs instead. hdfs dfs same as 2nd i.e would work for all the operations related to HDFS and is the recommended command instead of hadoop dfsbelow is the list categorized as HDFS commands.**#hdfs commands** namenode|secondarynamenode|datanode|dfs|dfsadmin|fsck|balancer|fetchdt|oiv|dfsgroupsSo even if you use Hadoop dfs , it will look locate hdfs and delegate that command to hdfs dfs
