When is uncoded transmission optimal? This paper derives easy-to-check necessary and suÆcient conditions that do not require nding the rate-distortion and the capacity-cost functions. We consider the symbol-by-symbol communication of discretetime memoryless sources across discrete-time memoryless channels, using single-letter coding and decoding. This is an optimal communication system if and o...

there is no doubt that colors are important factors in creating arts including poetry. the poets use them because of their visual beauties to show their hidden values. sometimes they go further – beyond the external features – ad use colors as symbols to express their own meaning. moreover, modern poet’s deep insight and vision are the main causes to change the colorful portrait to a bright won...

       The essential oils of the aerial parts of three different Artemisia species (A.scoparia, A. diffusa, A. turanica ) growing wildly in the northeast of Iran were analyzed by GC-MS. Twe...