Where to define nomenclature in a proposal or dissertation? I am writing my proposal and I am borrowing heavily from one of my publications. The published paper has a Nomenclature section at the very beginning (just after the abstract). 

What is the appropriate place for a nomenclature in a proposal/thesis? Or is it more advisable to explain the terms near the place where they are used (considering that if Nomenclature is published on a distant page it would be too much of an effort on the reader's part to scroll down and up again)?
I personally think the biggest consideration is how often the term or symbol is used. If it's used a lot, then a clear definition at the start is probably the best. The reader then knows where to look if they're unsure of the meaning rather than having to find the first place it's used, and it would be ridiculous to keep defining it every time you use it.

For things that are just used once, it may be more readable to define it at the point of use. The definition is only relevant for that little portion, so splitting the definition and use makes things, as you say, too much of an effort for the reader.

The question then is where to draw the line; at what point does a rarely used term become common enough to warrant being included in the nomenclature section? This is, I think, becomes a matter of preference. Personally, if a term were used in more than one section, I'd define it at the start. Though, if it really is only used twice, perhaps an in-place definition and a "recall that we define..." kind of sentence would read more smoothly.