This is a really short tutorial on how to fix the tiling effect that may occur when using particle systems, specifically smoke. I found this problem when trying to make a steam effect of Lava hitting water, which causes a large cloud of steam.
Alright so I am assuming you know how to use UDK to some degree, (since you are using particle systems).
Anyways I went ahead and got a UDK included smoke emitter which you can find by searching for "Smoke" under the particle systems. Its called: P_FX_SmokeColumn
*Note if you intend on keeping these settings for you map I recommend creating a copy of the effect in a new package, so you don't have package differences with anyone else working with UDK.
I also, added them to a default map to show the tiling that you may be experiencing.
(Left is the default emitter and the right is the scaled version with the tiling)
Now to get rid of this tiling, is very simple, go ahead and open the particle system (double click). Once open you should see two emitter pieces in a block box, the emitter itself, some properties and a graph.
Now if you happened to select a specific piece of the emitter just click the black region to the right side of ground smoke.
Now in the properties area there should be a tab specified Macro UV go ahead and open that to find the Macro UV Radius marked in red below. (which by default is 200)
This is what causes our tiling effect when the particle becomes too big, so we need to change it.
I changed mine to "2" and got the following effect:
A nice smooth looking smoke column.
I recommend that you play with the settings just to get use to what they do and what you are specifically looking for.
Hope someone will find it useful in the future I know I did! :D