trunk/doc/howto-units.lyx

#LyX 1.4.1 created this file. For more info see http://www.lyx.org/
\lyxformat 245
\begin_document
\begin_header
\textclass book
\language english
\inputencoding auto
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\papersize default
\use_geometry false
\use_amsmath 2
\cite_engine basic
\use_bibtopic false
\paperorientation portrait
\secnumdepth 3
\tocdepth 3
\paragraph_separation indent
\defskip medskip
\quotes_language english
\papercolumns 1
\papersides 1
\paperpagestyle default
\tracking_changes false
\output_changes true
\end_header

\begin_body

\begin_layout Chapter
Defining New Units of Measure
\begin_inset LatexCommand \label{cha:units}

\end_inset


\end_layout

\begin_layout Standard
Occasionally units of measure are needed that do not come predefined in
 the ASCEND system.
 You can define a new unit of measure by defining the conversion factor.
 In this chapter, we examine how to do this easily for an individual user
 and on a system-wide basis.
 
\end_layout

\begin_layout Section

\emph on
Caveats
\end_layout

\begin_layout Standard
\begin_inset Marginal
status collapsed

\begin_layout Standard
Order matters!
\end_layout

\end_inset

Order matters for defining units of measure in three ways.
\end_layout

\begin_layout Itemize
a unit of measure must be defined before it is used anywhere.
\end_layout

\begin_layout Itemize
the first definition ASCEND reads for a unit of measure is the only definition
 ASCEND sees.
\end_layout

\begin_layout Itemize
new units can be defined only from already defined units.
\end_layout

\begin_layout Standard
Measuring units are absolutely global in the ASCEND environment -- they
 are not deleted when the Library of types is deleted.
 Once you define a unit's conversion factor, you are stuck with it until
 you shut down and restart ASCEND.
 For any unit conversion definition, only the first conversion factor seen
 is accepted.
 Redefinitions of the same unit are ignored.
\end_layout

\begin_layout Standard
\begin_inset Marginal
status collapsed

\begin_layout Standard
Multiplicative unit conversions only!
\end_layout

\end_inset

The various units ASCEND uses are all obtained by conversion factors (multiplica
tion only) from the SI units.
 So, for example, temperatures may be in degrees Rankine but not in Fahrenheit.
 In this chapter we address creating new conversion factors.
 For handling non-
\end_layout

\begin_layout Standard
multiplicative conversions (such as the Fahrenheit or Celsius offsets) see
 Section\InsetSpace ~

\begin_inset LatexCommand \vref{sec:dimeqns.Fahrenheit}

\end_inset

.
\end_layout

\begin_layout Section
Individualised units
\end_layout

\begin_layout Standard
There are two scenarios for individualized units of measure.
 One in which you need a measure defined only for a specific model and another
 in which you want to define a measure that you will use throughout your
 modeling activities in the future.
 The syntax for both is the same, but where best to put the UNITS statement
 differs.
\end_layout

\begin_layout Subsection
Units of measure for a specific model
\end_layout

\begin_layout Standard
Units of measure that are used in only one model can be defined at the beginning
 of the model itself or before the model, but not the units appear in the
 model definition.
 Let us suppose you want to measure speed in {furlong/fortnight} in a model.
 ASCEND does not define 
\family typewriter
furlong
\family default
, 
\family typewriter
fortnight
\family default
, or 
\family typewriter
furlong/fortnight
\family default
.
 (Interestingly, we have been unable to find standard definitions for them!).
\end_layout

\begin_layout LyX-Code
MODEL mock_turtle;
\end_layout

\begin_layout LyX-Code
    d IS_A distance;
\end_layout

\begin_layout LyX-Code
    delta_t IS_A time;
\end_layout

\begin_layout LyX-Code
s IS_A speed
\end_layout

\begin_layout LyX-Code

\end_layout

\begin_layout LyX-Code
    s = d/delta_t;
\end_layout

\begin_layout LyX-Code
       (* We really should write s * delta_t = d;
\end_layout

\begin_layout LyX-Code
       to avoid division by zero.
 *)
\end_layout

\begin_layout LyX-Code

\end_layout

\begin_layout LyX-Code
UNITS
\end_layout

\begin_layout LyX-Code
    furlong = {3.17*kilometer};
\end_layout

\begin_layout LyX-Code
    fortnight = {10*day};
\end_layout

\begin_layout LyX-Code
END UNITS;
\end_layout

\begin_layout LyX-Code

\end_layout

\begin_layout LyX-Code
METHODS
\end_layout

\begin_layout LyX-Code
METHOD default_self;
\end_layout

\begin_layout LyX-Code
    d := 1 {furlong};
\end_layout

\begin_layout LyX-Code
    t := 5 {hours};
\end_layout

\begin_layout LyX-Code
END default_self;
\end_layout

\begin_layout LyX-Code
 
\end_layout

\begin_layout LyX-Code
(* other standard methods omitted *)
\end_layout

\begin_layout LyX-Code

\end_layout

\begin_layout LyX-Code
END mock_turtle;
\end_layout

\begin_layout Standard
In mock_turtle we define 
\family typewriter
furlong
\family default
 and 
\family typewriter
fortnight
\family default
 conversions 
\series bold
before
\series default
 they are used in the methods and before any equations which use them.
 Also, notice that, even though ASCEND rejects this model 
\family typewriter
mock_turtle
\family default
, as it will because of the missing "
\family typewriter
;
\family default
" after "speed" in the fourth line, 
\family typewriter
furlong
\family default
 and 
\family typewriter
fortnight
\family default
 still get defined.
 The 
\family typewriter
UNITS
\family default
 statement can appear in any context and gets processed regardless of any
 other errors in that context.
\end_layout

\begin_layout Subsection
UNITS OF MEASURE FOR ALL YOUR PERSONAL MODELS
\end_layout

\begin_layout Standard
If you commonly use a set of units that is not in the default ASCEND library
 
\family typewriter
measures.a4l
\family default
, you can create your own personal library of units in the user data directory
 
\family typewriter
ascdata
\family default
.
 The location of this directory is given by ASCEND at the end of all the
 start-up spew it prints to the Console window (or xterm under UNIX) as
 shown below.
 You will see a path other than 
\family typewriter
/usr0/ballan/
\family default
 of course.
\end_layout

\begin_layout LyX-Code
-----------------------------------
\end_layout

\begin_layout LyX-Code
User data directory is /usr0/ballan/ascdata
\end_layout

\begin_layout LyX-Code
-----------------------------------
\end_layout

\begin_layout Standard
Create the library file 
\family typewriter
myunits.a4l
\family default
 in your 
\family typewriter
ascdata
\family default
 directory.
 This file should contain a 
\family typewriter
UNITS
\family default
 statement and any comments or 
\family typewriter
NOTES
\family default
 you wish to make.
 This file should contain any conversions that you change often.
 For example:
\end_layout

\begin_layout LyX-Code
UNITS
\end_layout

\begin_layout LyX-Code
    (* Units for Norway, maybe?*)
\end_layout

\begin_layout LyX-Code
    euro = {1*currency};
\end_layout

\begin_layout LyX-Code
    (* currency is the fundamental financial unit *)
\end_layout

\begin_layout LyX-Code
    kroner = {0.00314*euro};
\end_layout

\begin_layout LyX-Code
    nk = {kroner};
\end_layout

\begin_layout LyX-Code
    USdollar = {0.9*euro};
\end_layout

\begin_layout LyX-Code
    CANdollar = {0.65*USdollar};
\end_layout

\begin_layout LyX-Code
END UNITS;
\end_layout

\begin_layout Standard
Note that this file contains a definition of 
\family typewriter
USdollar
\family default
 different from that given in the standard library 
\family typewriter
measures.a4l
\family default
.
 ASCEND will warn you about the conflict.
 You must load 
\family typewriter
myunits.a4l
\family default
 into ASCEND before 
\family typewriter
atoms.a4l
\family default
 or any of our higher level libraries.
 You can ensure that this happens by putting the statement
\end_layout

\begin_layout LyX-Code
REQUIRE "myunits.a4l";
\end_layout

\begin_layout Standard
on the very first line in all your model definition files.
\end_layout

\begin_layout Section
NEW SYSTEM-WIDE UNITS
\end_layout

\begin_layout Standard
Suppose you are maintaining ASCEND on a network of computers with many users.
 You have a standard set of models stored in a centrally located directory,
 and you want to define units for use by everyone on the network.
 In this case, just edit 
\family typewriter
models/measures.a4l
\family default
, the default units of measure library.
 ASCEND is an open system.
 
\end_layout

\begin_layout Standard
Make the new unit conversion definition statement(s) of the form
\end_layout

\begin_layout LyX-Code
newunit = {combination of old units};
\end_layout

\begin_layout Standard
as described in **Section 9.2.** In the file 
\family typewriter
measures.a4l
\family default
, add your statement(s) anywhere inside the block of definitions that starts
 with 
\family typewriter
UNITS
\family default
 and ends with 
\family typewriter
END UNITS
\family default
.
 The existing definitions are divided up into groups by comment statements.
 If your conversion belongs to one of the groups, it is best to put the
 conversion in that group.
 The groups are given in Table 
\begin_inset LatexCommand \ref{tab:units.groupOfUnits}

\end_inset

.
\end_layout

\begin_layout Standard
\begin_inset Float table
wide false
sideways false
status open

\begin_layout Caption
Groups of units in the current measures library
\begin_inset LatexCommand \label{tab:units.groupOfUnits}

\end_inset


\end_layout

\begin_layout Standard
\begin_inset Tabular
<lyxtabular version="3" rows="21" columns="1">
<features>
<column alignment="center" valignment="top" leftline="true" rightline="true" width="0">
<row topline="true" bottomline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Standard

\family typewriter
distance
\end_layout

\end_inset
</cell>
</row>
<row topline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Standard

\family typewriter
mass
\end_layout

\end_inset
</cell>
</row>
<row topline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Standard

\family typewriter
time
\end_layout

\end_inset
</cell>
</row>
<row topline="true" endhead="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Standard

\family typewriter
molecular quantities
\end_layout

\end_inset
</cell>
</row>
<row topline="true" endhead="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Standard

\family typewriter
money
\end_layout

\end_inset
</cell>
</row>
<row topline="true" endhead="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Standard

\family typewriter
reciprocal time (frequency)
\end_layout

\end_inset
</cell>
</row>
<row topline="true" endhead="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Standard

\family typewriter
area
\end_layout

\end_inset
</cell>
</row>
<row topline="true" endhead="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Standard

\family typewriter
volume
\end_layout

\end_inset
</cell>
</row>
<row topline="true" endhead="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Standard

\family typewriter
force
\end_layout

\end_inset
</cell>
</row>
<row topline="true" endhead="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Standard

\family typewriter
pressure
\end_layout

\end_inset
</cell>
</row>
<row topline="true" endhead="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Standard

\family typewriter
energy
\end_layout

\end_inset
</cell>
</row>
<row topline="true" endhead="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Standard

\family typewriter
power
\end_layout

\end_inset
</cell>
</row>
<row topline="true" endhead="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Standard

\family typewriter
absolute viscosity
\end_layout

\end_inset
</cell>
</row>
<row topline="true" endhead="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Standard

\family typewriter
electric charge
\end_layout

\end_inset
</cell>
</row>
<row topline="true" bottomline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Standard

\family typewriter
miscellaneous electromagnetic
\end_layout

\end_inset
</cell>
</row>
<row topline="true" bottomline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Standard

\family typewriter
swiped from C math.h
\end_layout

\end_inset
</cell>
</row>
<row topline="true" bottomline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Standard

\family typewriter
constant based conversions
\end_layout

\end_inset
</cell>
</row>
<row topline="true" bottomline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Standard

\family typewriter
subtly dimensionless measures
\end_layout

\end_inset
</cell>
</row>
<row topline="true" bottomline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Standard

\family typewriter
light quantities
\end_layout

\end_inset
</cell>
</row>
<row topline="true" bottomline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Standard

\family typewriter
miscellaneous rates
\end_layout

\end_inset
</cell>
</row>
<row topline="true" bottomline="true">
<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
\begin_inset Text

\begin_layout Standard

\family typewriter
time variant conversions
\end_layout

\end_inset
</cell>
</row>
</lyxtabular>

\end_inset


\end_layout

\end_inset


\end_layout

\begin_layout Section
Send them in
\end_layout

\begin_layout Standard
We are always on the lookout for useful unit conversions to add to 
\family typewriter
measures.a4l
\family default
.
 If you create a 
\family typewriter
myunits.a4l
\family default
 containing unit conversion definitions of general use (i.e.
 not currency exchange rates and other time-varying conversions), please
 mail us a copy and include your name in a comment.
 Thank you very much.
\end_layout

\end_body
\end_document
1	johnpye	825	#LyX 1.4.1 created this file. For more info see http://www.lyx.org/
2			\lyxformat 245
3			\begin_document
4			\begin_header
5			\textclass book
6			\language english
7			\inputencoding auto
8			\fontscheme default
9			\graphics default
10			\paperfontsize default
11			\spacing single
12			\papersize default
13			\use_geometry false
14			\use_amsmath 2
15			\cite_engine basic
16			\use_bibtopic false
17			\paperorientation portrait
18			\secnumdepth 3
19			\tocdepth 3
20			\paragraph_separation indent
21			\defskip medskip
22			\quotes_language english
23			\papercolumns 1
24			\papersides 1
25			\paperpagestyle default
26			\tracking_changes false
27			\output_changes true
28			\end_header
29
30			\begin_body
31
32			\begin_layout Chapter
33			Defining New Units of Measure
34			\begin_inset LatexCommand \label{cha:units}
35
36			\end_inset
37
38
39			\end_layout
40
41			\begin_layout Standard
42			Occasionally units of measure are needed that do not come predefined in
43			the ASCEND system.
44			You can define a new unit of measure by defining the conversion factor.
45			In this chapter, we examine how to do this easily for an individual user
46			and on a system-wide basis.
47
48			\end_layout
49
50			\begin_layout Section
51
52			\emph on
53			Caveats
54			\end_layout
55
56			\begin_layout Standard
57			\begin_inset Marginal
58			status collapsed
59
60			\begin_layout Standard
61			Order matters!
62			\end_layout
63
64			\end_inset
65
66			Order matters for defining units of measure in three ways.
67			\end_layout
68
69			\begin_layout Itemize
70			a unit of measure must be defined before it is used anywhere.
71			\end_layout
72
73			\begin_layout Itemize
74			the first definition ASCEND reads for a unit of measure is the only definition
75			ASCEND sees.
76			\end_layout
77
78			\begin_layout Itemize
79			new units can be defined only from already defined units.
80			\end_layout
81
82			\begin_layout Standard
83			Measuring units are absolutely global in the ASCEND environment -- they
84			are not deleted when the Library of types is deleted.
85			Once you define a unit's conversion factor, you are stuck with it until
86			you shut down and restart ASCEND.
87			For any unit conversion definition, only the first conversion factor seen
88			is accepted.
89			Redefinitions of the same unit are ignored.
90			\end_layout
91
92			\begin_layout Standard
93			\begin_inset Marginal
94			status collapsed
95
96			\begin_layout Standard
97			Multiplicative unit conversions only!
98			\end_layout
99
100			\end_inset
101
102			The various units ASCEND uses are all obtained by conversion factors (multiplica
103			tion only) from the SI units.
104			So, for example, temperatures may be in degrees Rankine but not in Fahrenheit.
105			In this chapter we address creating new conversion factors.
106			For handling non-
107			\end_layout
108
109			\begin_layout Standard
110			multiplicative conversions (such as the Fahrenheit or Celsius offsets) see
111			Section\InsetSpace ~
112
113			\begin_inset LatexCommand \vref{sec:dimeqns.Fahrenheit}
114
115			\end_inset
116
117			.
118			\end_layout
119
120			\begin_layout Section
121			Individualised units
122			\end_layout
123
124			\begin_layout Standard
125			There are two scenarios for individualized units of measure.
126			One in which you need a measure defined only for a specific model and another
127			in which you want to define a measure that you will use throughout your
128			modeling activities in the future.
129			The syntax for both is the same, but where best to put the UNITS statement
130			differs.
131			\end_layout
132
133			\begin_layout Subsection
134			Units of measure for a specific model
135			\end_layout
136
137			\begin_layout Standard
138			Units of measure that are used in only one model can be defined at the beginning
139			of the model itself or before the model, but not the units appear in the
140			model definition.
141			Let us suppose you want to measure speed in {furlong/fortnight} in a model.
142			ASCEND does not define
143			\family typewriter
144			furlong
145			\family default
146			,
147			\family typewriter
148			fortnight
149			\family default
150			, or
151			\family typewriter
152			furlong/fortnight
153			\family default
154			.
155			(Interestingly, we have been unable to find standard definitions for them!).
156			\end_layout
157
158			\begin_layout LyX-Code
159			MODEL mock_turtle;
160			\end_layout
161
162			\begin_layout LyX-Code
163			d IS_A distance;
164			\end_layout
165
166			\begin_layout LyX-Code
167			delta_t IS_A time;
168			\end_layout
169
170			\begin_layout LyX-Code
171			s IS_A speed
172			\end_layout
173
174			\begin_layout LyX-Code
175
176			\end_layout
177
178			\begin_layout LyX-Code
179			s = d/delta_t;
180			\end_layout
181
182			\begin_layout LyX-Code
183			(* We really should write s * delta_t = d;
184			\end_layout
185
186			\begin_layout LyX-Code
187			to avoid division by zero.
188			*)
189			\end_layout
190
191			\begin_layout LyX-Code
192
193			\end_layout
194
195			\begin_layout LyX-Code
196			UNITS
197			\end_layout
198
199			\begin_layout LyX-Code
200			furlong = {3.17*kilometer};
201			\end_layout
202
203			\begin_layout LyX-Code
204			fortnight = {10*day};
205			\end_layout
206
207			\begin_layout LyX-Code
208			END UNITS;
209			\end_layout
210
211			\begin_layout LyX-Code
212
213			\end_layout
214
215			\begin_layout LyX-Code
216			METHODS
217			\end_layout
218
219			\begin_layout LyX-Code
220			METHOD default_self;
221			\end_layout
222
223			\begin_layout LyX-Code
224			d := 1 {furlong};
225			\end_layout
226
227			\begin_layout LyX-Code
228			t := 5 {hours};
229			\end_layout
230
231			\begin_layout LyX-Code
232			END default_self;
233			\end_layout
234
235			\begin_layout LyX-Code
236
237			\end_layout
238
239			\begin_layout LyX-Code
240			(* other standard methods omitted *)
241			\end_layout
242
243			\begin_layout LyX-Code
244
245			\end_layout
246
247			\begin_layout LyX-Code
248			END mock_turtle;
249			\end_layout
250
251			\begin_layout Standard
252			In mock_turtle we define
253			\family typewriter
254			furlong
255			\family default
256			and
257			\family typewriter
258			fortnight
259			\family default
260			conversions
261			\series bold
262			before
263			\series default
264			they are used in the methods and before any equations which use them.
265			Also, notice that, even though ASCEND rejects this model
266			\family typewriter
267			mock_turtle
268			\family default
269			, as it will because of the missing "
270			\family typewriter
271			;
272			\family default
273			" after "speed" in the fourth line,
274			\family typewriter
275			furlong
276			\family default
277			and
278			\family typewriter
279			fortnight
280			\family default
281			still get defined.
282			The
283			\family typewriter
284			UNITS
285			\family default
286			statement can appear in any context and gets processed regardless of any
287			other errors in that context.
288			\end_layout
289
290			\begin_layout Subsection
291			UNITS OF MEASURE FOR ALL YOUR PERSONAL MODELS
292			\end_layout
293
294			\begin_layout Standard
295			If you commonly use a set of units that is not in the default ASCEND library
296
297			\family typewriter
298			measures.a4l
299			\family default
300			, you can create your own personal library of units in the user data directory
301
302			\family typewriter
303			ascdata
304			\family default
305			.
306			The location of this directory is given by ASCEND at the end of all the
307			start-up spew it prints to the Console window (or xterm under UNIX) as
308			shown below.
309			You will see a path other than
310			\family typewriter
311			/usr0/ballan/
312			\family default
313			of course.
314			\end_layout
315
316			\begin_layout LyX-Code
317			-----------------------------------
318			\end_layout
319
320			\begin_layout LyX-Code
321			User data directory is /usr0/ballan/ascdata
322			\end_layout
323
324			\begin_layout LyX-Code
325			-----------------------------------
326			\end_layout
327
328			\begin_layout Standard
329			Create the library file
330			\family typewriter
331			myunits.a4l
332			\family default
333			in your
334			\family typewriter
335			ascdata
336			\family default
337			directory.
338			This file should contain a
339			\family typewriter
340			UNITS
341			\family default
342			statement and any comments or
343			\family typewriter
344			NOTES
345			\family default
346			you wish to make.
347			This file should contain any conversions that you change often.
348			For example:
349			\end_layout
350
351			\begin_layout LyX-Code
352			UNITS
353			\end_layout
354
355			\begin_layout LyX-Code
356			(* Units for Norway, maybe?*)
357			\end_layout
358
359			\begin_layout LyX-Code
360			euro = {1*currency};
361			\end_layout
362
363			\begin_layout LyX-Code
364			(* currency is the fundamental financial unit *)
365			\end_layout
366
367			\begin_layout LyX-Code
368			kroner = {0.00314*euro};
369			\end_layout
370
371			\begin_layout LyX-Code
372			nk = {kroner};
373			\end_layout
374
375			\begin_layout LyX-Code
376			USdollar = {0.9*euro};
377			\end_layout
378
379			\begin_layout LyX-Code
380			CANdollar = {0.65*USdollar};
381			\end_layout
382
383			\begin_layout LyX-Code
384			END UNITS;
385			\end_layout
386
387			\begin_layout Standard
388			Note that this file contains a definition of
389			\family typewriter
390			USdollar
391			\family default
392			different from that given in the standard library
393			\family typewriter
394			measures.a4l
395			\family default
396			.
397			ASCEND will warn you about the conflict.
398			You must load
399			\family typewriter
400			myunits.a4l
401			\family default
402			into ASCEND before
403			\family typewriter
404			atoms.a4l
405			\family default
406			or any of our higher level libraries.
407			You can ensure that this happens by putting the statement
408			\end_layout
409
410			\begin_layout LyX-Code
411			REQUIRE "myunits.a4l";
412			\end_layout
413
414			\begin_layout Standard
415			on the very first line in all your model definition files.
416			\end_layout
417
418			\begin_layout Section
419			NEW SYSTEM-WIDE UNITS
420			\end_layout
421
422			\begin_layout Standard
423			Suppose you are maintaining ASCEND on a network of computers with many users.
424			You have a standard set of models stored in a centrally located directory,
425			and you want to define units for use by everyone on the network.
426			In this case, just edit
427			\family typewriter
428			models/measures.a4l
429			\family default
430			, the default units of measure library.
431			ASCEND is an open system.
432
433			\end_layout
434
435			\begin_layout Standard
436			Make the new unit conversion definition statement(s) of the form
437			\end_layout
438
439			\begin_layout LyX-Code
440			newunit = {combination of old units};
441			\end_layout
442
443			\begin_layout Standard
444			as described in Section 9.2. In the file
445			\family typewriter
446			measures.a4l
447			\family default
448			, add your statement(s) anywhere inside the block of definitions that starts
449			with
450			\family typewriter
451			UNITS
452			\family default
453			and ends with
454			\family typewriter
455			END UNITS
456			\family default
457			.
458			The existing definitions are divided up into groups by comment statements.
459			If your conversion belongs to one of the groups, it is best to put the
460			conversion in that group.
461			The groups are given in Table
462			\begin_inset LatexCommand \ref{tab:units.groupOfUnits}
463
464			\end_inset
465
466			.
467			\end_layout
468
469			\begin_layout Standard
470			\begin_inset Float table
471			wide false
472			sideways false
473			status open
474
475			\begin_layout Caption
476			Groups of units in the current measures library
477			\begin_inset LatexCommand \label{tab:units.groupOfUnits}
478
479			\end_inset
480
481
482			\end_layout
483
484			\begin_layout Standard
485			\begin_inset Tabular
486			<lyxtabular version="3" rows="21" columns="1">
487			<features>
488			<column alignment="center" valignment="top" leftline="true" rightline="true" width="0">
489			<row topline="true" bottomline="true">
490			<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
491			\begin_inset Text
492
493			\begin_layout Standard
494
495			\family typewriter
496			distance
497			\end_layout
498
499			\end_inset
500			</cell>
501			</row>
502			<row topline="true">
503			<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
504			\begin_inset Text
505
506			\begin_layout Standard
507
508			\family typewriter
509			mass
510			\end_layout
511
512			\end_inset
513			</cell>
514			</row>
515			<row topline="true">
516			<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
517			\begin_inset Text
518
519			\begin_layout Standard
520
521			\family typewriter
522			time
523			\end_layout
524
525			\end_inset
526			</cell>
527			</row>
528			<row topline="true" endhead="true">
529			<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
530			\begin_inset Text
531
532			\begin_layout Standard
533
534			\family typewriter
535			molecular quantities
536			\end_layout
537
538			\end_inset
539			</cell>
540			</row>
541			<row topline="true" endhead="true">
542			<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
543			\begin_inset Text
544
545			\begin_layout Standard
546
547			\family typewriter
548			money
549			\end_layout
550
551			\end_inset
552			</cell>
553			</row>
554			<row topline="true" endhead="true">
555			<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
556			\begin_inset Text
557
558			\begin_layout Standard
559
560			\family typewriter
561			reciprocal time (frequency)
562			\end_layout
563
564			\end_inset
565			</cell>
566			</row>
567			<row topline="true" endhead="true">
568			<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
569			\begin_inset Text
570
571			\begin_layout Standard
572
573			\family typewriter
574			area
575			\end_layout
576
577			\end_inset
578			</cell>
579			</row>
580			<row topline="true" endhead="true">
581			<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
582			\begin_inset Text
583
584			\begin_layout Standard
585
586			\family typewriter
587			volume
588			\end_layout
589
590			\end_inset
591			</cell>
592			</row>
593			<row topline="true" endhead="true">
594			<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
595			\begin_inset Text
596
597			\begin_layout Standard
598
599			\family typewriter
600			force
601			\end_layout
602
603			\end_inset
604			</cell>
605			</row>
606			<row topline="true" endhead="true">
607			<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
608			\begin_inset Text
609
610			\begin_layout Standard
611
612			\family typewriter
613			pressure
614			\end_layout
615
616			\end_inset
617			</cell>
618			</row>
619			<row topline="true" endhead="true">
620			<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
621			\begin_inset Text
622
623			\begin_layout Standard
624
625			\family typewriter
626			energy
627			\end_layout
628
629			\end_inset
630			</cell>
631			</row>
632			<row topline="true" endhead="true">
633			<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
634			\begin_inset Text
635
636			\begin_layout Standard
637
638			\family typewriter
639			power
640			\end_layout
641
642			\end_inset
643			</cell>
644			</row>
645			<row topline="true" endhead="true">
646			<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
647			\begin_inset Text
648
649			\begin_layout Standard
650
651			\family typewriter
652			absolute viscosity
653			\end_layout
654
655			\end_inset
656			</cell>
657			</row>
658			<row topline="true" endhead="true">
659			<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
660			\begin_inset Text
661
662			\begin_layout Standard
663
664			\family typewriter
665			electric charge
666			\end_layout
667
668			\end_inset
669			</cell>
670			</row>
671			<row topline="true" bottomline="true">
672			<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
673			\begin_inset Text
674
675			\begin_layout Standard
676
677			\family typewriter
678			miscellaneous electromagnetic
679			\end_layout
680
681			\end_inset
682			</cell>
683			</row>
684			<row topline="true" bottomline="true">
685			<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
686			\begin_inset Text
687
688			\begin_layout Standard
689
690			\family typewriter
691			swiped from C math.h
692			\end_layout
693
694			\end_inset
695			</cell>
696			</row>
697			<row topline="true" bottomline="true">
698			<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
699			\begin_inset Text
700
701			\begin_layout Standard
702
703			\family typewriter
704			constant based conversions
705			\end_layout
706
707			\end_inset
708			</cell>
709			</row>
710			<row topline="true" bottomline="true">
711			<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
712			\begin_inset Text
713
714			\begin_layout Standard
715
716			\family typewriter
717			subtly dimensionless measures
718			\end_layout
719
720			\end_inset
721			</cell>
722			</row>
723			<row topline="true" bottomline="true">
724			<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
725			\begin_inset Text
726
727			\begin_layout Standard
728
729			\family typewriter
730			light quantities
731			\end_layout
732
733			\end_inset
734			</cell>
735			</row>
736			<row topline="true" bottomline="true">
737			<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
738			\begin_inset Text
739
740			\begin_layout Standard
741
742			\family typewriter
743			miscellaneous rates
744			\end_layout
745
746			\end_inset
747			</cell>
748			</row>
749			<row topline="true" bottomline="true">
750			<cell alignment="center" valignment="top" topline="true" leftline="true" rightline="true" usebox="none">
751			\begin_inset Text
752
753			\begin_layout Standard
754
755			\family typewriter
756			time variant conversions
757			\end_layout
758
759			\end_inset
760			</cell>
761			</row>
762			</lyxtabular>
763
764			\end_inset
765
766
767			\end_layout
768
769			\end_inset
770
771
772			\end_layout
773
774			\begin_layout Section
775			Send them in
776			\end_layout
777
778			\begin_layout Standard
779			We are always on the lookout for useful unit conversions to add to
780			\family typewriter
781			measures.a4l
782			\family default
783			.
784			If you create a
785			\family typewriter
786			myunits.a4l
787			\family default
788			containing unit conversion definitions of general use (i.e.
789			not currency exchange rates and other time-varying conversions), please
790			mail us a copy and include your name in a comment.
791			Thank you very much.
792			\end_layout
793
794			\end_body
795			\end_document