Fast Reaction, Slow Diffusion, and Curve Shortening 论文

1989SIAM Journal on Applied Mathematics引用 302
Advanced Mathematical Modeling in EngineeringNonlinear Partial Differential EquationsDifferential Equations and Numerical Methods

摘要

</head> <body lang=3DES link=3Dblue vlink=3Dpurple style=3D'tab-interval:35.4pt'> <div class=3DSection1> <p class=3DMsoNormal align=3Dcenter style=3D'margin-left:18.0pt;text-align:center'><b style=3D'mso-bidi-font-weight:normal'><span lang=3DEN-US style=3D'mso-ansi-language: EN-US'>RESUMEN<o:p></o:p></span></b> </div> <p class=3DMsoNormal style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span style=3D'color:white'><span style=3D'display:none;mso-hide:all'><!--[if gte vml 1]><v:shapetype id=3D"_x0000_t75" coordsize=3D"21600,21600" o:spt=3D"75" o:preferrelative=3D"t" path=3D"m@4@5l@4@11@9@11@9@5xe" filled=3D"f" stroked=3D"f"> <v:stroke joinstyle=3D"miter"/> <v:formulas> <v:f eqn=3D"if lineDrawn pixelLineWidth 0"/> <v:f eqn=3D"sum @0 1 0"/> <v:f eqn=3D"sum 0 0 @1"/> <v:f eqn=3D"prod @2 1 2"/> <v:f eqn=3D"prod @3 21600 pixelWidth"/> <v:f eqn=3D"prod @3 21600 pixelHeight"/> <v:f eqn=3D"sum @0 0 1"/> <v:f eqn=3D"prod @6 1 2"/> <v:f eqn=3D"prod @7 21600 pixelWidth"/> <v:f eqn=3D"sum @8 21600 0"/> <v:f eqn=3D"prod @7 21600 pixelHeight"/> <v:f eqn=3D"sum @10 21600 0"/> </v:formulas> <v:path o:extrusionok=3D"f" gradientshapeok=3D"t" o:connecttype=3D"rect"/> <o:lock v:ext=3D"edit" aspectratio=3D"t"/> </v:shapetype><v:shape id=3D"_x0000_i1027" type=3D"#_x0000_t75" style=3D'width:1in; height:18pt'> <v:imagedata src=3D"RESUMEN_archivos/image001.wmz" o:title=3D""/> </v:shape><![endif]--><![if !vml]><img width=3D96 height=3D24 src=3D"RESUMEN_archivos/image002.gif" v:shapes=3D"_x0000_i1027"><![endif]></span><span style=3D'display:none;mso-hide:all'><!--[if gte vml 1]><v:shape id=3D"_x0000_i1026" type=3D"#_x0000_t75" style=3D'width:1in;height:18pt'> <v:imagedata src=3D"RESUMEN_archivos/image003.wmz" o:title=3D""/> </v:shape><![endif]--><![if !vml]><img width=3D96 height=3D24 src=3D"RESUMEN_archivos/image004.gif" v:shapes=3D"_x0000_i1026"><![endif]></span><span style=3D'display:none;mso-hide:all'><!--[if gte vml 1]><v:shape id=3D"_x0000_i1025" type=3D"#_x0000_t75" style=3D'width:1in;height:18pt'> <v:imagedata src=3D"RESUMEN_archivos/image005.wmz" o:title=3D""/> </v:shape><![endif]--><![if !vml]><img width=3D96 height=3D24 src=3D"RESUMEN_archivos/image006.gif" v:shapes=3D"_x0000_i1025"><![endif]></span></span><span class=3DSpellE>The</span> <span class=3DSpellE>reaction</span>-<span class=3DSpellE>diffusion</span> <span class=3DSpellE>problem</span> <p class=3DMsoNormal align=3Dcenter style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt: auto;text-align:center'><span class=3DSpellE><i style=3D'mso-bidi-font-style:normal'>U</i><sub>t</sub></span><sub> </sub>=3D <a name=3D"OLE_LINK19"></a><a name=3D"OLE_LINK18"><span style=3D'mso-bookmark: OLE_LINK19'>&#949;</span></a> &#8710; <i style=3D'mso-bidi-font-style:normal'>U - <a name=3D"OLE_LINK33"></a><a name=3D"OLE_LINK32"><span style=3D'mso-bookmark:OLE_LINK33'><span style=3D'mso-spacerun:yes'> </span></span></a></i><a name=3D"OLE_LINK27"></a><a name=3D"OLE_LINK24"></a><a name=3D"OLE_LINK21"></a><a name=3D"OLE_LINK20"><span style=3D'mso-bookmark:OLE_LINK21'><span style=3D'mso-bookmark:OLE_LINK24'><span style=3D'mso-bookmark:OLE_LINK27'><span style=3D'mso-bookmark:OLE_LINK33'><span style=3D'mso-bookmark:OLE_LINK32'>&#949;</span></span></span></span></span></a><span style=3D'mso-bookmark:OLE_LINK33'><span style=3D'mso-bookmark:OLE_LINK32'> </span></span><sup>-1 </sup><span class=3DSpellE>V<sub>u</sub></span><sub> </sub>(u), u (x, 0, <a name=3D"OLE_LINK29"></a><a name=3D"OLE_LINK28"><span style=3D'mso-bookmark:OLE_LINK29'>&#949;</span></a>) =3D g (x), <a name=3D"OLE_LINK23"></a><a name=3D"OLE_LINK22"><span style=3D'mso-bookmark: OLE_LINK23'>ð</span></a> <sub>n</sub> u =3D 0 <span class=3DSpellE>on</span> <a name=3D"OLE_LINK31"></a><a name=3D"OLE_LINK30"><span style=3D'mso-bookmark:OLE_LINK31'>ð </span></a><a name=3D"OLE_LINK26"></a><a name=3D"OLE_LINK25"><span style=3D'mso-bookmark:OLE_LINK26'><span style=3D'mso-bookmark:OLE_LINK31'><span style=3D'mso-bookmark:OLE_LINK30'>&#937;</span></span></span></a><span style=3D'mso-bookmark:OLE_LINK31'><span style=3D'mso-bookmark:OLE_LINK30'></span></span> <span style=3D'mso-bookmark:OLE_LINK30'></span><span style=3D'mso-bookmark:OLE_LINK31'></span> <p class=3DMsoNormal style=3D'mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span class=3DGramE><span lang=3DEN-US style=3D'mso-ansi-language:EN-US'>for</span></span><span lang=3DEN-US style=3D'mso-ansi-language:EN-US'> a vector u( x, t, </span>&#949;<span lang=3DEN-US style=3D'mso-ansi-language:EN-US'>) is considered in a domain </span>&#937;<span style=3D'mso-ansi-language:EN-US'> <span style=3D'mso-spacerun:yes'> </span><span lang=3DEN-US>€ R <sup>m</sup>. An asymptotic solution is constructed for </span></span>&#949;<span style=3D'mso-ansi-language:EN-US'> <span lang=3DEN-US>small. It shows that at each x, u tends quickly to a minimum of <span class=3DGramE>V(</span> u ). When V has several minima, u tends to a piecewise constant function. Boundary layer expansions are constructed around the resulting surfaces of discontinuity or fronts. Each front is found to move along its normal with a constant velocity determined by the discontinuity <span class=3DGramE>[ V</span> ] in V across it. When <span class=3DGramE>[ V</span> ] =3D 0, the front's normal velocity is </span></span>&#949;<span style=3D'mso-ansi-language:EN-US'> <i style=3D'mso-bidi-font-style:normal'><span lang=3DEN-US>k</span></i><span lang=3DEN-US>, where <i style=3D'mso-bidi-font-style: normal'>k</i> <span style=3D'mso-spacerun:yes'> </span>is its mean curvature. The motion of fronts in this manner is studied for arcs in the plane which are normal to ð </span></span>&#937;<span style=3D'mso-ansi-language:EN-US'> <span lang=3DEN-US>at their endpoints, and for fronts that are closed curves. It is shown a front can shrink to a point in a finite time or tend to a locally shortest diameter <span class=3DGramE>of <span style=3D'mso-spacerun:yes'> </span><span lang=3DES style=3D'mso-ansi-language:ES'>&#937;</span></span>. In the latter case, a <span class=3DSpellE>nonconstant</span> steady state <i style=3D'mso-bidi-font-style: normal'>u </i><span class=3DGramE>( x</span>, &#8734;, </span></span>&#949;<span lang=3DEN-US style=3D'mso-ansi-language:EN-US'>) results. </span><span lang=3DEN-US style=3D'font-size:8.0pt;font-family:Arial;display:none;mso-hide:all;mso-ansi-language: EN-US'>P</span><span style=3D'font-size:8.0pt;font-family:Arial;display:none; mso-hide:all'>rincipio del formulario<o:p></o:p></span> </div> </div> </body> </html>