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Laurent Dumas & Zaid Dauhoo Laboratoire de Mathématiques de Versailles, Université de Versailles Saint Quentin en Yvelines Numerical Optimization and applications (MA2600) Lecture 1: Derivative Free Optimization (DFO) Numerical Optimization and applications, ECP 2013

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(i)Minimal molecular energy (ii) Construction of an optical fiber with optimal properties (iii) Debluring and denoising of a barcode image (iv) Car shape optimization Part 1: three DFO problems Numerical Optimization and applications, ECP 2013

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Goal: find the position of N atoms minimizing the Lennard Jones potential of the associated molecular: V( r )=1/r 12 – 2/r 6 for 2 atoms at a distance r. N=4 atomsN=7 atoms Numerical Optimization and applications, ECP 2013 (i) Minimal molecular energy

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> Such filters can be obtained by using an optical fiber called FBG (Fiber Bragg Grating) having a fast periodic modulation of its refractive index in the core: > The index variation can be optimized in order to give the desired reflectivity spectrum: inverse problem m (reflectivity spectrum) (ii) Construction of an optical fiber with optimal properties Numerical Optimization and applications, ECP 2013

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The refractive index of a FBG is expressed through a quasi-sinusoïdal function in the longitudinal direction z: n(z)=n 0 + n(z) cos(2 z/ 0 ) z [0, L] with the following notations: n 0 : index refraction of the core 0 : nominal period of the FBG n(z): slowly varying amplitude (also called apodisation) The inverse-type optimization problem will consist in finding the ‘best’ apodisation function leading to the desired reflectivity spectrum. (ii) Construction of an optical fiber with optimal properties Numerical Optimization and applications, ECP 2013

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The reflectivity spectrum is a function R( ) =| r( ) | 2 where r( ) = b B (0, ) / b F (0, ) In the above expression, the enveloppes of the forward and backward propagating waves are obtained by the resolution of the following system of coupled ODE’s: where, and (ii) Construction of an optical fiber with optimal properties Numerical Optimization and applications, ECP 2013

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(iii) Debluring and denoising of a barcode image Goal: identify a barcode from a blurred barcode image Code à 13 chiffres Numerical Optimization and applications, ECP 2013

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among which, 65% to 70 % depends on the exterior shape… …among which 90 % depends on the rear shape at 20 km/h, oil consumption is due to : Goal: find the optimal rear shape of a car with respect to its drag coefficient (iv) Car shape optimization Numerical Optimization and applications, ECP 2013

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Ford T: 0.8 (1908) Hummer H2: 0.57 (2003) Citroën SM: 0.33 (1970) Peugeot 407: 0.29 (2004) and… Tatra T77: (1935) (iv) Car shape optimization Numerical Optimization and applications, ECP 2013

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(i) Nelder Mead algorithm (1965) (ii) Multi Direction Search method (1989) Part 2: two DFO algorithms Numerical Optimization and applications, ECP 2013

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