Wavelets

[Do Dinh Nghia <don@iem.pw.edu.pl>]

Hi All !
 
 
 
 Sau khi nha^n. ddu*o*c. mail cua? anh So*n ve^` va^'n dde^` Wavelets , to^i co' may` mo` tim` tre^n ma.ng nhu*~ng sources ve^` va^'n dde^` na`y va` tha^'y      ra(ng` co' kha' nhie^`u sites vie^'t ve^` va^'n dde^` na`y . Trong site cu?a    Amara Graps (http://www.amara.com/current/wavelet.html) co' mo^.t article       vie^'t ve^` Wavelet ma` to^i cho la` ddo.c tu*o*ng ddo^is de^~ hie^?u vi`       cho tha^'y "the significant physical interpretation of wavelets " :
  " The fundamental idea behind wavelets is to analize according to scale         .....
  Approximation using superposition of functions has existed since the early     1800's , when J.Fourier discovered that he could superpose sines and cosines to represent other functions.However,in wavelet analysis, the scale that one uses in looking at data plays a special role.Wavelet algorithms process data at different scales or resolutions...".
  Nhu* va^y. ne^u' Fourier nhi`n ti'n hie^.u qua ca'c "O^'ng ki'nh" (ma` Amara  go.i la` "windows") co' ta^`n so^' kha'c nhau cua? ha`m co* so* sine , thi` trong wavelet analizing ti'n hie^.u ddu*o*c. soi qua ca'c "o^ng' ki'nh" co' ddo^.   ne't kha'c nhau . Vi' nhu* ta nhi`n mo^.t va^.t mo^.t ca'ch toa`n ca?nh va`     nhi`n ba(ng` ki'nh lu'p ca'c ddu*o*ng` ne't cu?a no'.\
 Ro~ ra`ng , khi pha^n ti'ch ti'n hie^.u trong frequence domain Fourier chi?    du`ng mo^t. "o^'ng ki'nh" (xe't ve^` phu*o*ng die^.n scaling) co`n wavelet      pha^n ti'ch ti'n hie^.u ba(`ng ca? mo^.t set "o^'ng ki'nh" , thi` kha? na(ng    xa^'p xi? ho'a (approximation) cua? wavelet la` chi'nh xa'c ho*n , nha^'t la`   khi xa^'p xi? ho'a choppy signals.
 Ve^` software implementation of wavelets thi` cu~ng co' nhie^`u location       cung ca^'p ( co' ca? Free) nhu* WAVELAB 701 cua? Stanford University , Wavelet  ToolBox cua? MathWorks,WaveLib cua? INT(France),... 
 Ne^'u co' ba.n na`o quan ta^m dde^'n va^'n dde^` na`y co' the^? Subcribe to theWavelet Digest (Free) ba(ng` ca'ch gu*i? mo^.t empty message  to add@wavelet.orgXin ca'm o*n su*. chu' y' cua? ca'c ba.n . Ta.m bie^t.!
 
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