There is a membrane made of an isotropic material whose elastic modulus and Poisson's ratios are E and v, respectively. When this membrane is elongated along x-direction with no lateral deformation in y-direction, the apparent elastic modulus (E') determined by measured values of stress and strain Sigma_x and Epsilon_x) should be greater than the material's own modulus (E) due to Poisson's effect. Determine the percentage difference between E' and E.