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| 6 | <title>PALM chapter 3.8</title> |
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| 11 | <meta name="AUTHOR" content="Siegfried Raasch"> |
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| 28 | |
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| 29 | <h3 style="line-height: 100%;">3.8 Coupled model runs</h3> |
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| 30 | |
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| 31 | <p style="line-height: 100%;">Starting from version 3.4 |
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| 32 | PALM allows coupled atmosphere-ocean model runs. By analogy with the |
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| 33 | modular structure of PALM, <span style="font-weight: bold;">mrun</span> |
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| 34 | starts the coupled model as two concurrent executables, the atmosphere |
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| 35 | version and the ocean version of PALM.</p> |
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| 36 | |
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| 37 | <p style="line-height: 100%;">Currently, the coupler |
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| 38 | is at an experimental stage using a simple MPI2 intercommunicator that |
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| 39 | matches the atmosphere and ocean processors one-to-one. This approach |
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| 40 | has limited flexibility and performance, because it requires |
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| 41 | identical horizontal numerical grids and it uses the same number of |
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| 42 | atmosphere and ocean processors, which does not necessarily guarrantee |
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| 43 | a good load balancing.</p> |
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| 44 | |
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| 45 | <p style="line-height: 100%;">The coupler establishes a |
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| 46 | one-way interaction between the |
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| 47 | atmosphere and the ocean. The atmosphere sends its bottom surface |
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| 48 | fluxes |
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| 49 | (temperature, humidity, momentum) to the ocean. The ocean sends its top |
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| 50 | surface temperature to the atmosphere. The atmosphere assumes |
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| 51 | saturation of humidity and zero wind speed at its bottom surface. For |
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| 52 | calculations with <a href="chapter_4.1.html#humidity">humidity</a> |
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| 53 | = .T. the atmospheric evaporation leads to a salinity flux in the ocean |
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| 54 | (see e.g. Steinhorn 1991, JPO 21, p. 1681).</p> |
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| 55 | |
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| 56 | <p style="line-height: 100%;">The full MPI-2 |
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| 57 | standard must be available in order to use the coupling, and it must be |
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| 58 | activated by adding the preprocessor directive <tt><font style="font-size: 10pt;" size="2">-D__mpi2</font></tt> |
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| 59 | to <tt><font style="font-size: 10pt;" size="2">cpp_options</font></tt> |
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| 60 | in the .mrun.config configuration file. (Note: MPI-2 is |
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| 61 | not available for the IBM-Regatta systems.) To start a |
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| 62 | coupled model run, |
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| 63 | this must be requested with the <b>mrun</b> option <tt><font style="font-size: 10pt;" size="2">-Y</font>.</tt> |
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| 64 | This tells <span style="font-weight: bold;">mrun</span> |
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| 65 | to start two PALM executables. Coupled runs are only possible in |
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| 66 | parallel mode, which means that the <b>mrun</b> option <tt><font style="font-size: 10pt;" size="2">-K parallel</font></tt> |
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| 67 | must also be set. The <b>mrun</b> call |
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| 68 | for coupled runs has to include the following coupling-related options: |
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| 69 | </p> |
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| 70 | |
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| 71 | <ul> |
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| 72 | |
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| 73 | <p style="line-height: 100%;"><tt><font style="font-size: 10pt;" size="2">mrun </font></tt><font style="font-size: 10pt;" size="2">...</font><tt><font style="font-size: 10pt;" size="2"> -K parallel -r |
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| 74 | “d3# d3o# </font></tt><font style="font-size: 10pt;" size="2">...</font><tt><font style="font-size: 10pt;" size="2">”</font></tt><tt><font style="font-size: 10pt;" size="2"> </font></tt><tt><font style="font-size: 10pt;" size="2">-X </font></tt><font style="font-size: 10pt;" size="2">...</font><tt><font style="font-size: 10pt;" size="2"> -Y</font></tt><tt>.</tt></p> |
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| 75 | |
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| 76 | </ul> |
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| 77 | |
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| 78 | <p style="line-height: 100%;">The <tt><font style="font-size: 10pt;" size="2">-X </font></tt><font style="font-size: 10pt;" size="2">...</font><tt><font style="font-size: 10pt;" size="2"> </font></tt>option |
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| 79 | here specifies the total number of processors assigned to the coupled |
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| 80 | model. Currently, half of them are assigned to each of the two coupled |
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| 81 | executables. Therefore it is advisable to specify an even number |
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| 82 | with <tt><font style="font-size: 10pt;" size="2">-X </font></tt><font style="font-size: 10pt;" size="2">...</font><tt> |
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| 83 | </tt>. Otherwise, in case of an odd total number of processors, |
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| 84 | one processor remains idle.</p> |
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| 85 | |
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| 86 | <p style="line-height: 100%;">Each coupled executable has |
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| 87 | its own, unique set of I/O filenames; <a href="chapter_3.4.html#coupled">chapter 3.4</a> gives |
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| 88 | information on file name conventions of coupled runs. The configuration |
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| 89 | file .mrun.config has to be extended for coupled runs. It is |
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| 90 | recommended to duplicate existing file connection identifiers such as |
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| 91 | "d3#", "pr#" etc. using the coupled ocean filenames accordingly. For |
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| 92 | example, the example of the previous chapters could be |
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| 93 | duplicated as follows:</p> |
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| 94 | |
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| 95 | <pre style="line-height: 100%;"><a href="chapter_3.4.html#PARIN"><font style="font-size: 10pt;" size="2">PARIN</font></a><font style="font-size: 10pt;" size="2"> in:job:npe d3# ~/palm/current_version/JOBS/$fname/INPUT _p3d</font><br><font style="font-size: 10pt;" size="2">PARIN in:job:npe d3f ~/palm/current_version/JOBS/$fname/INPUT _p3df</font><br><a href="chapter_3.4.html#BININ"><font style="font-size: 10pt;" size="2">BININ</font></a><font style="font-size: 10pt;" size="2"> in:loc d3f ~/palm/current_version/JOBS/$fname/OUTPUT _d3d</font><br><font style="font-size: 10pt;" size="2">#</font><br><a href="chapter_3.4.html#BINOUT"><font style="font-size: 10pt;" size="2">BINOUT</font></a><font style="font-size: 10pt;" size="2"> out:loc restart ~/palm/current_version/JOBS/$fname/OUTPUT _d3d<br>#</font><br><a href="chapter_3.4.html#RUN_CONTROL"><font style="font-size: 10pt;" size="2">RUN_CONTROL</font></a><font style="font-size: 10pt;" size="2"> out:loc:tr d3# ~/palm/current_version/JOBS/$fname/MONITORING _rc</font><br><a href="chapter_3.4.html#HEADER"><font style="font-size: 10pt;" size="2">HEADER</font></a><font style="font-size: 10pt;" size="2"> out:loc:tr d3# ~/palm/current_version/JOBS/$fname/MONITORING _header</font><br><a href="chapter_3.4.html#PLOT1D_PAR"><font style="font-size: 10pt;" size="2">PLOT1D_PAR</font></a><font style="font-size: 10pt;" size="2"> out:loc:tr pr# ~/palm/current_version/JOBS/$fname/OUTPUT _pr_par</font><br><a href="chapter_3.4.html#PLOT1D_DATA"><font style="font-size: 10pt;" size="2">PLOT1D_DATA</font></a><font style="font-size: 10pt;" size="2"> out:loc:tr pr# ~/palm/current_version/JOBS/$fname/OUTPUT _pr_in<br>#<br></font><font style="font-size: 10pt;" size="2">PARIN</font><font style="font-size: 10pt;" size="2"><span style="font-weight: bold;">_O</span> in:job:npe d3<span style="font-weight: bold;">o</span># ~/palm/current_version/JOBS/$fname/INPUT <span style="font-weight: bold;">_</span></font><font style="font-size: 10pt;" size="2"><span style="font-weight: bold;">o</span>_</font><font style="font-size: 10pt;" size="2">p3d</font><br><font style="font-size: 10pt;" size="2">PARIN<span style="font-weight: bold;">_O</span> in:job:npe d3<span style="font-weight: bold;">o</span>f ~/palm/current_version/JOBS/$fname/INPUT <span style="font-weight: bold;">_</span></font><font style="font-size: 10pt;" size="2"><span style="font-weight: bold;">o</span>_</font><font style="font-size: 10pt;" size="2">p3df</font><br><font style="font-size: 10pt;" size="2">BININ</font><font style="font-size: 10pt;" size="2"><span style="font-weight: bold;">_O</span> in:loc d3<span style="font-weight: bold;">o</span>f ~/palm/current_version/JOBS/$fname/OUTPUT <span style="font-weight: bold;">_</span></font><font style="font-size: 10pt;" size="2"><span style="font-weight: bold;">o</span>_</font><font style="font-size: 10pt;" size="2">d3d</font><br><font style="font-size: 10pt;" size="2">#</font><br><font style="font-size: 10pt;" size="2">BINOUT</font><font style="font-size: 10pt;" size="2"><span style="font-weight: bold;">_O</span> out:loc restart ~/palm/current_version/JOBS/$fname/OUTPUT <span style="font-weight: bold;">_</span></font><font style="font-size: 10pt;" size="2"><span style="font-weight: bold;">o</span>_</font><font style="font-size: 10pt;" size="2">d3d</font><br><font style="font-size: 10pt;" size="2">#</font><br><font style="font-size: 10pt;" size="2">RUN_CONTROL<span style="font-weight: bold;">_O</span></font><font style="font-size: 10pt;" size="2"> out:loc:tr d3<span style="font-weight: bold;">o</span># ~/palm/current_version/JOBS/$fname/MONITORING <span style="font-weight: bold;">_</span></font><font style="font-size: 10pt;" size="2"><span style="font-weight: bold;">o</span>_</font><font style="font-size: 10pt;" size="2">rc</font><br><font style="font-size: 10pt;" size="2">HEADER</font><font style="font-size: 10pt;" size="2"><span style="font-weight: bold;">_O</span> out:loc:tr d3<span style="font-weight: bold;">o</span># ~/palm/current_version/JOBS/$fname/MONITORING <span style="font-weight: bold;">_</span></font><font style="font-size: 10pt;" size="2"><span style="font-weight: bold;">o</span>_</font><font style="font-size: 10pt;" size="2">header</font><br><font style="font-size: 10pt;" size="2">PLOT1D_PAR<span style="font-weight: bold;">_O</span></font><font style="font-size: 10pt;" size="2"> out:loc:tr pr<span style="font-weight: bold;">o</span># ~/palm/current_version/JOBS/$fname/OUTPUT <span style="font-weight: bold;">_</span></font><font style="font-size: 10pt;" size="2"><span style="font-weight: bold;">o</span>_</font><font style="font-size: 10pt;" size="2">pr_par</font><br><font style="font-size: 10pt;" size="2">PLOT1D_DATA</font><font style="font-size: 10pt;" size="2"><span style="font-weight: bold;">_O</span> out:loc:tr pr<span style="font-weight: bold;">o</span># ~/palm/current_version/JOBS/$fname/OUTPUT <span style="font-weight: bold;">_</span></font><font style="font-size: 10pt;" size="2"><span style="font-weight: bold;">o</span>_</font><font style="font-size: 10pt;" size="2">pr_in</font><br></pre> |
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| 96 | |
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| 97 | <p style="line-height: 100%;">The coupled ocean model |
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| 98 | filenames in the first column (e.g.<font style="font-size: 10pt;" size="2"><span style="font-family: mon;"> </span><a href="chapter_3.4.html#PARIN">PARIN_O</a></font>) must |
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| 99 | be specified as given in <a href="chapter_3.4.html#coupled">chapter |
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| 100 | 3.4</a>; the file connection identifiers (e.g. <font style="font-size: 10pt;" size="2">d3o#</font>) |
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| 101 | and the file name extension (e.g. <font style="font-size: 10pt;" size="2"><span style="font-weight: bold;"><span style="font-family: mon;"></span></span>_</font><font style="font-size: 10pt;" size="2">o_</font><font style="font-size: 10pt;" size="2">p3d</font>) |
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| 102 | may be changed at the user's discretion.</p> |
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| 103 | |
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| 104 | <p style="line-height: 100%;">The coupler requires the |
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| 105 | following parameters to be equal in both <a href="chapter_3.4.html#PARIN"><font style="font-size: 10pt;" size="2"><span style="font-family: mon;"></span>PARIN</font></a> |
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| 106 | and <a href="chapter_3.4.html#PARIN"><font style="font-size: 10pt;" size="2">PARIN_O</font></a>: |
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| 107 | <a href="chapter_4.1.html#dx">dx</a>, <a href="chapter_4.1.html#dy">dy</a>, <a href="chapter_4.1.html#nx">nx</a>, <a href="chapter_4.1.html#ny">ny</a>, <a href="chapter_4.2.html#dt_coupling">dt_coupling</a>, <a href="chapter_4.2.html#end_time">end_time</a>, <a href="chapter_4.2.html#restart_time">restart_time</a>, |
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| 108 | <a href="chapter_4.2.html#dt_restart">dt_restart</a>. |
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| 109 | In the coupled atmosphere executable, <a href="chapter_4.2.html#bc_pt_b">bc_pt_b</a> is |
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| 110 | internally set and does not need to be prescribed; in the coupled ocean |
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| 111 | executable, <a href="chapter_4.2.html#bc_uv_t">bc_uv_t</a> is |
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| 112 | internally set ('neumann') and does not need to be prescribed. The |
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| 113 | coupled ocean parameter file <a href="chapter_3.4.html#PARIN"><font style="font-size: 10pt;" size="2">PARIN_O</font></a> |
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| 114 | should include dummy REAL value assignments to both <a href="chapter_4.1.html#top_momentumflux_u">top_momentumflux_u</a> |
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| 115 | and <a href="chapter_4.1.html#top_momentumflux_v">top_momentumflux_v</a> |
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| 116 | (e.g. top_momentumflux_u = 0.0, top_momentumflux_v = 0.0) to |
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| 117 | enable the momentum flux coupling.</p> |
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| 118 | |
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| 119 | <p style="line-height: 100%;">The coupling interval <a href="chapter_4.2.html#dt_coupling">dt_coupling</a> |
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| 120 | must be explicity set. In order to ensure synchronous coupling |
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| 121 | throughout the simulation, <a href="chapter_4.2.html#dt_coupling">dt_coupling</a> |
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| 122 | should be chosen larger than |
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| 123 | <a href="chapter_4.2.html#dt_max">dt_max</a>.</p> |
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| 124 | |
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| 125 | <hr> |
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| 126 | <p style="line-height: 100%;"><br> |
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| 127 | |
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| 128 | <font color="#000080"><font color="#000080"><a href="chapter_3.7.html"><font color="#000080"><img style="border: 2px solid ; width: 32px; height: 32px;" alt="" src="left.gif" name="Grafik1"></font></a><a href="index.html"><font color="#000080"><img src="up.gif" name="Grafik2" align="bottom" border="2" height="32" width="32"></font></a><a href="chapter_4.0.html"><font color="#000080"><img src="right.gif" name="Grafik3" align="bottom" border="2" height="32" width="32"></font></a></font></font></p> |
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| 129 | |
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| 130 | <p style="line-height: 100%;"><i>Last |
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| 131 | change: </i> $Id: chapter_3.8.html 115 2007-10-10 15:34:38Z letzel $</p> |
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