EE5410 Signal Processing : C/D conversion

EE5410 Signal Processing : C/D conversion

1. It is helpful to represent C/D as a process of periodic sampling followed by a mapping of the impulse train to a sequence.

2. In the first step, representing the sampling process, the impulse train xp(t) corresponds to a sequence if impulses with amplitudes corresponding to the samples of xc(t) and with a time spacing EQUAL to the sampling period T.

3. In the conversion from the impulse train to the discrete-time sequence, we obtain xd[n], corresponding to the SAME sequence of samples of xc(t), but with UNITY spacing in terms of the new independent variable n.

4. Thus, in effect, the conversion from the impulse train sequence of samples to the discrete-time sequence of samples can be thought of as a normalization in time.

stroboscopic effect : Depending on the frequency of flash, the element appears motionless or rotating in reverse direction.

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

六四-- 陳雲 - 包袱

由於六四是影響香港人心靈的大事，北京的中共、香港的土共乃至一 些政治投機的和事佬，不時都勸香港人放下六四的「 包袱」。

包袱一詞，被中共和土共用得久了，有了貶義，是精神負累、思想障礙之意，要完成思想改造，成為與 共黨同路的新人物，必須卸去自己的舊包袱，輕身上陣。

昔時，要動身遠行，必須要預備包袱，打點行裝，行得倦了，到了客店，打開包袱，裏面 是衣物、水囊、乾糧、碗筷、蠟燭、火鐮、針線、錢財、書信、賬本之類。

假如六四是包袱，裏面裝的就是良知、智慧與勇敢，是支持香港人共同遠行的精神資糧。 包袱好得很，怎會是壞東西？

http://forum9.hkgolden.com/view.aspx?type=CA&message=3052611