ex) simple

Simple is composed of two syllables:
sim and ple. In phonetic symble, 'ple' doesn't have a vowel, but it seems to be considered as a syllable. Do you have a technical term for that?
Is it 'syllable consonant'?

It is a syllable. Syllables do not require vowels, but often has them. I learned quite alot on the structure of syllables here:

http://en.wikipedia.org/wiki/Syllable

The technical term for a syllable that ends in a consonant, like in the word "simple," is a "closed syllable."

In a closed syllable, the vowel is followed by one or more consonants, which "closes" the syllable. The consonant at the end of the syllable does not start a new syllable but instead makes the previous vowel shorter.

In the word "simple," the syllable division is between the "i" and the "m" (sim-ple). The "e" at the end of the word is part of the closed syllable, even though it does not have a vowel sound.