Recent posts to bloghttps://sourceforge.net/u/mbradle/blog/Recent posts to blogenFri, 02 Dec 2016 13:25:32 -0000Updating the reaction data for network calculations discussionhttps://sourceforge.net/u/mbradle/blog/2012/09/updating-the-reaction-data-for-network-calculations/<div class="markdown_content"><p>I've moved this to the <a class="" href="https://sourceforge.net/p/nucnet-tools/discussion/help/thread/cd3f3020/">discussion</a> board.</p></div>Bradley S. MeyerFri, 02 Dec 2016 13:25:32 -0000https://sourceforge.net3f9b66c0acb4ddb008d49c717d83443f3d5acc44Updating the reaction data for network calculations discussionhttps://sourceforge.net/u/mbradle/blog/2012/09/updating-the-reaction-data-for-network-calculations/<div class="markdown_content"><p>Dear Dr.Meyer<br/>
I wanna know something about the beta minus decay rates of those extreme neutron-rich nuclei in the my_net.xml file for the network calculation.So, from what model are they obtained? </p></div>Bradley S. MeyerFri, 02 Dec 2016 09:34:48 -0000https://sourceforge.netf41c8253f30a6c902aa57aafd70604f6fe7d844aChanging input conditions for our first network calculation discussionhttps://sourceforge.net/u/mbradle/blog/2012/07/changing-input-conditions-for-our-first-network-calculation/<div class="markdown_content"><p>Thanks for your post. Screening can be handled as described in this <a class="" href="https://sourceforge.net/u/mbradle/blog/2016/05/including-electron-screening-in-a-network-calculation/">post</a>. There are other posts on electron screening--search the blog for <em>screening</em>.</p>
<p>As for the <em>tau</em>, setting it to <em>inf</em> means that the temperature and density will not change during the calculation. In reality, the core of the Sun contracts during its lifetime. You could model this by choosing a <em>tau</em> of, say, -3.15e17 (note the minus sign to make contraction, not expansion). Of course to get a more realistic description of the behavior, you would need a full stellar model. I hope this helps. Best wishes.</p></div>Bradley S. MeyerThu, 06 Oct 2016 12:40:55 -0000https://sourceforge.nete6e7bf974c8c5e29f48c68723cff1a8a8722c44fChanging input conditions for our first network calculation discussionhttps://sourceforge.net/u/mbradle/blog/2012/07/changing-input-conditions-for-our-first-network-calculation/<div class="markdown_content"><p>Dear Sir<br/>
Thanks For your helpful post, i have couple of questions<br/>
First, how can we consider the electron screening ?? <br/>
and Secound what is the best value of tau in the Sun ??<br/>
Thanks</p></div>Bradley S. MeyerThu, 06 Oct 2016 10:57:51 -0000https://sourceforge.net0038f79501e0693164962f6a2be8d90f48a628b7Modifying calculation input with NucNet Tools example codes discussionhttps://sourceforge.net/u/mbradle/blog/2012/07/modifying-calculation-input-with-nucnet-tools-example-codes/<div class="markdown_content"><p>Thanks for your question. The temperature and density I chose for this calculation were appropriate for CNO burning and not for the burning in the Sun (see this <a class="" href="https://sourceforge.net/u/mbradle/blog/2012/07/test/">post</a> for conditions more appropriate for the Sun). CNO burning occurs in stars with mass larger than the Sun. In the calculation in the present post, the 10<sup>8</sup> years is arbitrarily chosen, As the figure above shows, this duration is long enough for all the hydrogen to burn to helium when the temperature is T<sub>9</sub> = 30. This helps explain why massive stars have shorter lifetimes than the Sun. I hope this helps. Best wishes.</p></div>Bradley S. MeyerMon, 03 Oct 2016 11:38:30 -0000https://sourceforge.net330237326c0525083e835dbe9ab3afef1b7885d1Modifying calculation input with NucNet Tools example codes discussionhttps://sourceforge.net/u/mbradle/blog/2012/07/modifying-calculation-input-with-nucnet-tools-example-codes/<div class="markdown_content"><p>Dear Brad,<br/>
I quote "We now have an input zone file that has Solar mass fractions and appropriate properties. These properties are: initial time step dt = 10-5 seconds, tend (calculation duration) of 3.15 x 1015 seconds = 108 years, infinite tau (expansion timescale) so that the calculation is static, neutrino chemical potential of -infinity so that neutrinos are freely streaming and escape, temperature of t9 = 0.03, that is, 30 million Kelvins, density of 15 g/cc, and steps = 5 so that we print out every 5 timesteps."</p>
<p>If we want to calculate the mass fractions for the sun TODAY, <strong>should (and could) one use tend = 4.5 Gyr = 3.1536x1016 seconds?</strong> The limitation to 3.15x1015 (108y) is not clear for me.<br/>
Thank you in advance</p></div>Bradley S. MeyerMon, 03 Oct 2016 08:19:00 -0000https://sourceforge.net5b4979dd6c96e4e6640b23f6aa02dfaebc709169Compiling NucNet Tools with the clang and gcc compilers on a mac discussionhttps://sourceforge.net/u/mbradle/blog/2016/07/compiling-nucnet-tools-with-the-clang-and-gcc-compilers-on-a-mac/<div class="markdown_content"><p>When uninstalling boost with macports, it may be denied because of the packages depending on boost. To solve this problem one can do </p>
<p><code>sudo port uninstall --follow-dependents boost</code> </p>
<p>as described <a class="" href="https://guide.macports.org/chunked/using.html#using.port.uninstall" rel="nofollow">here</a>.</p></div>Tianhong YuSun, 25 Sep 2016 03:25:40 -0000https://sourceforge.net4a6244636ec671dc11c792d9b5f5cd622ef4b3ecCalculating nuclear statistical equilibrium discussionhttps://sourceforge.net/u/mbradle/blog/2012/09/calculating-nuclear-statistical-equilibrium/<div class="markdown_content"><p>Thanks for your post. Of course the abundances in the center of the Sun are not in nuclear statistical equilibrium (NSE)--the nuclear reaction timescales at <em>T<sub>9</sub> = 0.015</em>, <em>ρ = 150 g/cc</em>, and <em>Y<sub>e</sub> = 0.5</em> are so long that achieving NSE would require a time longer than the Sun will live. Moreover, if the abundances were in NSE, the center of the Sun would be at an energy minimum and any further reactions would require net energy input to proceed.</p>
<p>Neverthess, you can compute the abundances that would result if the abundance distribution in the center of the Sun were miraculously to convert to NSE. To do that, you can use the JINA <a class="" href="https://sourceforge.net/u/mbradle/blog/2012/07/understanding-the-nuclear-physics-data-for-network-calculations/">nuclear data</a> file. To do this, type</p>
<p><strong>cd nucnet-tools-code/examples/network</strong></p>
<p><strong>make data</strong></p>
<p>This will download the data, and in particular, the file <em>data_pub/my_net.xml</em>, which has the masses, spins, and partition function information for the species of interest. Now you can run the NSE code. Type</p>
<p><strong>cd ../../build</strong></p>
<p><strong>make -f Makefile.libnuceq all_libnuceq</strong></p>
<p>This creates the libnuceq example codes. Now run the calculation by typing</p>
<p><strong>cd ../libnuceq</strong></p>
<p><strong>./compute_nse ../data_pub/my_net.xml 0.015 150 0.5</strong></p>
<p>You will find that the abundances are completely dominated by <em><sup>56</sup>Ni</em>, which is the species with the highest binding energy per nucleon for <em>Y<sub>e</sub> = 0.5</em>. Of course <em><sup>56</sup>Ni</em> is radioactive, so that species would immediately start decaying (which will change <em>Y<sub>e</sub></em>) and the system would evolve until it reached <em><sup>56</sup>Fe</em>--for more information, see the libnuceq technical report <a class="" href="https://sourceforge.net/p/libnuceq/wiki/Home/">low-temperature nuclear statistical equilibrium</a>.</p>
<p>If you need to create your own nuclear data, you can use the libnucnet example code <em>create_nuc_xml_from_text</em> to convert appropriately formatted text data to XML. This <a class="" href="https://sourceforge.net/u/mbradle/blog/2013/10/extending-partition-function-data-to-higher-temperatures/">post</a> might also be of interest.</p>
<p>I hope all this helps. Best wishes.</p></div>Bradley S. MeyerSat, 24 Sep 2016 13:39:33 -0000https://sourceforge.net82c5ea39e388bd97f4f217fcc95e3fb298aefe79Calculating nuclear statistical equilibrium discussionhttps://sourceforge.net/u/mbradle/blog/2012/09/calculating-nuclear-statistical-equilibrium/<div class="markdown_content"><p>Dear Brad<br/>
I am trying to reproduce the standard solar model values using this post<br/>
i.e we should run <strong>" ./compute_nse ../data_pub/ZZZ.xml 0.015 1.5e2 0.5"</strong> <br/>
This would mean that we have to calculate the partition function using a previous post <strong><em>Studying the nuclear partition function</em></strong> and create a new input file similar to ../data_pub/example_nuc.xml.<br/>
Firstly, does this make sens and if yes how can I do that (create my ZZZ.xml file)?</p></div>Bradley S. MeyerFri, 23 Sep 2016 12:22:11 -0000https://sourceforge.net22f5f8224de7e63d4ed0b1549711ef563d131d74test discussionhttps://sourceforge.net/u/mbradle/blog/2012/07/test/<div class="markdown_content"><p>I've discussed this with you in person. You confirm that this was due to a lack of adequate internet connection, and when the connection was better, the problem was solved. Best wishes.</p></div>Bradley S. MeyerWed, 24 Aug 2016 13:04:28 -0000https://sourceforge.net485179c8a1f8bb6ea8aa7812a6cffcc97b7385c0