<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>1409-2433</journal-id>
<journal-title><![CDATA[Revista de Matemática Teoría y Aplicaciones]]></journal-title>
<abbrev-journal-title><![CDATA[Rev. Mat]]></abbrev-journal-title>
<issn>1409-2433</issn>
<publisher>
<publisher-name><![CDATA[Centro de Investigaciones en Matemática Pura y Aplicada (CIMPA) y Escuela de Matemática, San José, Costa Rica.]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S1409-24332014000100004</article-id>
<title-group>
<article-title xml:lang="en"><![CDATA[On the design of membranes with increasing fundamental frequency]]></article-title>
<article-title xml:lang="es"><![CDATA[Sobre el diseño de membranas con frecuencia fundamental creciente]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[González De Paz]]></surname>
<given-names><![CDATA[Raúl B.]]></given-names>
</name>
<xref ref-type="aff" rid="A01"/>
</contrib>
</contrib-group>
<aff id="A01">
<institution><![CDATA[,Universidad del Valle de Guatemala Departamento de Matematicas ]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
<country>Guatemala</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>06</month>
<year>2014</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>06</month>
<year>2014</year>
</pub-date>
<volume>21</volume>
<numero>1</numero>
<fpage>56</fpage>
<lpage>72</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.sa.cr/scielo.php?script=sci_arttext&amp;pid=S1409-24332014000100004&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.sa.cr/scielo.php?script=sci_abstract&amp;pid=S1409-24332014000100004&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.sa.cr/scielo.php?script=sci_pdf&amp;pid=S1409-24332014000100004&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[By means of a relaxation approach, we study the shape design of a stiff inclusion with given area in a membrane in order to maximize its fundamental frequency. As an eigenvalue control problem, the fundamental frequency is a concave function of the control, which is not described by the membrane shape, but by an element in a function space. First order optimality conditions allow to describe the optimal shape by means of a free boundary value problem.]]></p></abstract>
<abstract abstract-type="short" xml:lang="es"><p><![CDATA[Mediante un método de relajación, se estudia la forma de una inclusión rígida de área dada en una membrana de manera que se maximice su frecuencia fundamental. Analizado como un problema de control de valores propios, la frecuencia fundamental es una función cóncava del control, el cual no es descrito por la forma de la membrana, sino por un elemento de un espacio de funciones. Las condiciones de optimalidad de primer orden permiten describir la forma óptima mediante un problema de frontera libre.]]></p></abstract>
<kwd-group>
<kwd lng="en"><![CDATA[variational methods for eigenvalues]]></kwd>
<kwd lng="en"><![CDATA[shape optimization]]></kwd>
<kwd lng="en"><![CDATA[free boundary value problems.]]></kwd>
<kwd lng="es"><![CDATA[métodos variacionales para valores propios]]></kwd>
<kwd lng="es"><![CDATA[optimización de forma]]></kwd>
<kwd lng="es"><![CDATA[problemas de frontera libre.]]></kwd>
</kwd-group>
</article-meta>
</front><body><![CDATA[ <div style="text-align: justify; font-family: Verdana;">     <div style="text-align: center;"><font style="font-weight: bold;"  size="4"> On the design of membranes with increasing fundamental frequency</font>    <br> </div> <font size="2"></font>    <br>     <div style="text-align: center;"><font style="font-weight: bold;"  size="4">Sobre el dise&ntilde;o de membranas con frecuencia fundamental creciente</font>    <br>     <br> <font size="2"></font></div>     <div style="text-align: center;"><font size="2">Ra&uacute;l B. Gonz&aacute;lez De Paz<a href="#1">*</a></font><a name="2"></a>+    <br> </div> <font size="2"></font>    <br> <small><a name="Correspondencia2"></a>*<a href="#Correspondencia1">Direcci&oacute;n para correspondencia</a></small><a href="#Correspondencia1">:</a>    ]]></body>
<body><![CDATA[<br> <hr style="width: 100%; height: 2px;"><font size="2"></font><font  style="font-weight: bold;" size="3">Abstract</font>    <br> <font size="2"></font>    <br> <font size="2">By means of a relaxation approach, we study the shape design of a stiff inclusion with given area in a membrane in order to maximize its fundamental frequency. As an eigenvalue control problem, the fundamental frequency is a concave function of the control, which is not described by the membrane shape, but by an element in a function space. First order optimality conditions allow to describe the optimal shape by means of a free boundary value problem.</font>    <br> <font size="2"></font>    <br> <font size="2"><span style="font-weight: bold;">Keywords</span>: variational methods for eigenvalues, shape optimization, free boundary value problems.</font>    <br> <font size="2"></font>    <br> <font style="font-weight: bold;" size="3">Resumen</font>    <br> <font size="2"></font>    <br> <font size="2">Mediante un m&eacute;todo de relajaci&oacute;n, se estudia la forma de una inclusi&oacute;n r&iacute;gida de &aacute;rea dada en una membrana de manera que se maximice su frecuencia fundamental. Analizado como un problema de control de valores propios, la frecuencia fundamental es una funci&oacute;n c&oacute;ncava del control, el cual no es descrito por la forma de la membrana, sino por un elemento de un espacio de funciones. Las condiciones de optimalidad de primer orden permiten describir la forma &oacute;ptima mediante un problema de frontera libre.</font>    <br> <font size="2"></font>    ]]></body>
<body><![CDATA[<br> <font size="2"><span style="font-weight: bold;">Palabras clave</span>: m&eacute;todos variacionales para valores propios, optimizaci&oacute;n de forma, problemas de frontera libre.</font>    <br>     <br> <font size="2"><span style="font-weight: bold;">Mathematics Subject Classification</span>: 35J20, 35R35, 49R05, 49Q10.</font>    <br> <hr style="width: 100%; height: 2px;"><font size="2"></font><font  style="font-weight: bold;" size="3">    <br> </font><small><font size="3"><small>Ver contenido disponible en pdf</small></font></small><font  style="font-weight: bold;" size="3">    <br>     <br> </font> <hr style="width: 100%; height: 2px;"><font style="font-weight: bold;"  size="3">References</font>    <br> <font size="2"></font>    <!-- ref --><br> <font size="2">[1] Bourbaki, N. (1973) <span  style="font-style: italic;">Espaces Vectoriels Topologiques</span>. Hermann, Paris.    &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[&#160;<a href="javascript:void(0);" onclick="javascript: window.open('/scielo.php?script=sci_nlinks&ref=1958182&pid=S1409-2433201400010000400001&lng=','','width=640,height=500,resizable=yes,scrollbars=1,menubar=yes,');">Links</a>&#160;]<!-- end-ref --></font>    ]]></body>
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<body><![CDATA[<br> <font size="2"><a name="1"></a><a href="#2">*</a>Departamento de Matematicas, Universidad del Valle de Guatemala, Apdo. Postal 82, 01901 Guatemala, Guatemala. E-Mail: ragopa@ufm.edu</font>    <br> <hr style="width: 100%; height: 2px;">     <div style="text-align: center;"><font style="font-weight: bold;"  size="2">Received: 30/Jan/2013; Revised: 8/Nov/2013; Accepted: 15/Nov/2013 </font></div> </div>      ]]></body><back>
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