Annoying default author name

Hi all am a new bie for WP two days back i set up my blog with my hoster..
the problem was that i changed all the details to fit my own need but i cant find a way out to change the text “Howdy! I’m Denis and this is my blog.” which is displayed near by my photo(author photo)
pls visit my site to get a clear view power of php
how can change this text to my need like Its prakash’s blog

is there some thing i want to change the php coding in any of the file of word press i even tried to find this string in that but tiered after searching for two or three files..or i have to change any file in the theme directory??? (my theme is from devart)
pls give me a solution to solve this
my mail id is(( stbalaji2u at gmail dot com))