Difference in whitespace around section head from mkII to mkIV

Difference in whitespace around section head from mkII to mkIV

[Adam Fuller]

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hi all,
i'm experiencing some unwanted whitespace related to a section head.  the whitespace is present when using lua (texexec --lua funk.tex) and absent when using mkII (texexec funk.tex).  i've confirmed the correct mkII behaviour on the garden's live tool, and my own minimals installation:
This is LuaTeX, Version beta-0.60.1-2010050621 (rev 3678)
  \write18 enabled.
(funk.tex

ConTeXt  ver: 2010.05.13 12:15 MKIV  fmt: 2010.5.21  int: english/english

if you run the document below on mkII, you'll see that the first text on each slide is right up against the top of the text area.  this is good.  if you use my version of luatex, a line is skipped.  why the difference?  i'm not actually using anything lua (i've just started using Context in the past weeks, and i've got a conference presentation due in 3 days, so i've got weird habits.  i'm just now getting my head around the copious amounts of documentation for the system, and all the differences between context, luatex, pdftex, mkII, mkIV, and all the other new terms), so i'll probably just "texexec funk.tex" as a workaround.  /however/, when i get some free time, i'll be playing with lua, and i'd like it to work right.  i've been a latex user since my undergrad a couple of years ago, and
  i just found metapost maybe one month ago.  what an eye opener!  i love programming and i love making dorky little vector images... it's the perfect marriage!

maybe somebody bright can shed some light on this?

thanks everybody,
adam


% author: adam fuller
% date: 24/5/2010
% description: why does placehead=no,page=yes in \definehead push
% the first line of a slide down by one?  when a slide is too long
% and breaks to another page, that page starts right up at the top,
% without the annoying extra whitespace.  trying to unravel it.

\setupheadertexts[myslide][]
\setupheader[state=start]
\setuppagenumbering[state=stop]

\definehead[myslide][subsubsection]
\setuphead[myslide][style=slanted,placehead=no,page=yes]
\definestartstop[slide][
	before={\page\startalignment[right,nothyphenated,hanging]\tf},
	after={\stopalignment}]

\starttext
\showframe[text]%
\showframe[header]%
\myslide{}%
\midaligned\framed[location=middle,align=center,offset=none,frame=off]{
	%\blank[2*big,force]
	{\bfa Adam Fuller}
	\blank[1*big,force]
	{\em from}
	\blank[1*big,force]
	{\bfa U. Canterbury}
	\blank[1*big,force]
	{\em talks about}
	\blank[1*big,force]
	{\bfa Adapting simplified propeller turbines to higher specific
	speeds: CFD studies}
	\blank[1*big,force]
	{\em at}
	\blank[1*big,force]
	{\bfa Hidroenergia 2010}
}
\page%
\myslide{Where I start from}%
My Ph.D. research has been to increase the specific speed ($N_S$),
starting with an existing range, while maintaining a turbine
efficiency of 70\%.

By \em{adapting}, I mean taking an existing design \em{philosophy} to a
new design \em{point}.

This \em{philosophy} is just a list of rules that reflect the
turbines' intended use:
\startitemize
	\item no guide vanes
	\item run at 1500~rev/min only
	\item use flat blades
\stopitemize


\myslide{New design point, new challenges}
The paper discusses how increasing the specific speed may impact on
the design of such a turbine's three main components.

The adapted version of each component brings its own challenges.

At higher $N_S$
\startitemize
	\item draft tube performance is increasingly
important.  How sensitive is its performance to the inputs in this
particular case?
	\item velocity triangles at the runner's leading and trailing
edge become less forgiving to uncertainty (dimensional and fluid
dynamical)
	\item the volute's priority changes from \quote{provide swirl
$x$} to \quote{provide uniform axial flow at mimimum loss}.  How
must the design change?
\stopitemize

\myslide{For this presentation}
To illuminate these three points, I worked up a CFD study related
to each component.  To summarize the studies:
\startitemize
	\item Draft tube: $C_p = f({\rm swirl}, \theta)$.  What is $f$?
I'll try to put my result in the context of the literature.
	\item Runner: from the desktop-design stage, the ratios
	\startformula
		\omega r:V_a:\Delta V_t\approx 8:4:1,
	\stopformula
	are expected to cause problems with sensitivity of output and
	efficiency to speed.  I'll talk about how my CFD results suprised
me.
	\item Volute: Trying to reconcile the need for predictable axial
runner inlet flow, low loss, and no flow-spanning vanes or struts
has led to an adaptation of previous Giddens volutes.  I'll talk
about the changes that were made, and show that the new volute
looks to meet the requirements.
\stopitemize
\stoptext

[-- Attachment #2: adam_fuller.vcf --]
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begin:vcard
fn:Adam Fuller
n:Fuller;Adam
org:University of Canterbury;Mechanical Engineering
adr:Private Bag 4800;;Intersection of Creyke Rd and Engineering Rd;Christchurch;Canterbury;8041;New Zealand
email;internet:adam.fuller@pg.canterbury.ac.nz
title:Ph.D. candidate
tel;work:(+64) 3 364 2987 ext. 8390
tel;fax:(+64) 3 364 2078
tel;home:(+64) 3 366 3455
tel;cell:(+64) 21 0254 8677
url:http://www.mech.canterbury.ac.nz/
version:2.1
end:vcard


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