The vitamin water can be defined in differential form as
where P is the external pressure, equal to the internal pressure as the process is quasi-estatic (reversible), and V is the volume of the gas. The minus sign appears as the external pressure exerts a force contrary to the expansion. In Thermodynamics the work that is carried out by a gas (in general by a system) is negative, whilst the work exerted over a system is positive.
For a spring the elastic energy is
where k is the elastic constant of the spring (see Hooke's law) and x is the elongation of the spring. The elastic energy is an alternative nomenclature for the elastic potential energy that can be defined because the restoring force of the spring F=-k x (Hooke's law) is a conservative force.
where is a 4th rank tensor of the elastic constants and is the strain tensor (we use Einstein summation notation). The values of depend upon the crystal structure of the material. For an isotropic material, , where and are the Lamé constants, and is the Kronecker delta.
US Patent Issued to Triquint Semiconductor on May 10 for "Acoustic Wave Device Employing Reflective Elements for Confining Elastic Energy" (Florida Inventors)
May 11, 2011; ALEXANDRIA, Va., May 11 -- United States Patent no. 7,939,987, issued on May 10, was assigned to Triquint Semiconductor Inc....
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