# Questions about de_min in octave

7 messages
Open this post in threaded view
|

## Questions about de_min in octave

 1- I have a function with 3 parameters  [x(1),x(2),x(3)] and I try to solve minimum of that function and try to get optimal  [x(1),x(2),x(3)] I know the upper and lower bound of that parameters but there shoud be also some constrains like x(3)=>x(2) I can not define that constrain and solution shows me x(2)>x(3) sometime. How can I implement  x(3)=>x(2) for all possible iteration of de_min. 2-Sometimes convergence parameter shows 0 but "optimal" parameters out of bound. Thanks -- Sent from: http://octave.1599824.n4.nabble.com/Octave-General-f1599825.html_______________________________________________ Help-octave mailing list [hidden email] https://lists.gnu.org/mailman/listinfo/help-octave
Open this post in threaded view
|

## Re: Questions about de_min in octave

 On Thu, Sep 28, 2017 at 3:34 AM, denizyazgac wrote:1- I have a function with 3 parameters  [x(1),x(2),x(3)] and I try to solve minimum of that function and try to get optimal  [x(1),x(2),x(3)] I know the upper and lower bound of that parameters but there shoud be also some constrains like x(3)=>x(2) I can not define that constrain and solution shows me x(2)>x(3) sometime. How can I implement  x(3)=>x(2) for all possible iteration of de_min. 2-Sometimes convergence parameter shows 0 but "optimal" parameters out of bound. Thanks _Can you show us the function?-- DAS _______________________________________________ Help-octave mailing list [hidden email] https://lists.gnu.org/mailman/listinfo/help-octave
Open this post in threaded view
|

## Re: Questions about de_min in octave

 In reply to this post by denizyazgac On Thu, Sep 28, 2017 at 3:34 AM, denizyazgac wrote:1- I have a function with 3 parameters without any details of the functions you're using or have written, it's impossible for us to help. Octave has an optimization package that may do some of the tasks you want. link to the function list below.  the functions should define how to provide variables, constraints, etc.https://octave.sourceforge.io/optim/overview.html _______________________________________________ Help-octave mailing list [hidden email] https://lists.gnu.org/mailman/listinfo/help-octave
Open this post in threaded view
|

## Re: Questions about de_min in octave

 This post was updated on . Sorry; I try to make a back calculation with using Johnson Champoux Allard mathematical model, which defines acoustic impedance behaviour of acoustic foams. f,RRR,III vectors are measured data(frequency,real and imaginer parts) from impedance tube (they are surface impedance), I try to obtain some critical parameters like tortousity,char. viscous and thermal length from this data with de_min function.   #back_calclation for porous samples clc clear all pkg load optim gamma=1.401 # specific heat ratio P0=99700 #pressure eta= 1.56E-5; #dynamic viscosity B=0.707 # Prandtl number fi=0.95 # porosity     L=34.35/1000 #thickness rho0=1.2 #air density sigma=8197# air resistivity c=340;# sound speed f=[202.53 300.94 399.35 502.52 599.34 704.10 800.92 897.74 1002.50 1100.91 1204.09 1305.67 1404.09 1500.92 1604.09]; RRR=[0.731942065 0.701451715 0.641506283 0.596238299 0.580492187 0.535207505 0.504733852 0.48898774 0.473158139 0.457395329 0.471037507 0.469968842 0.468933572 0.497370082 0.496284719]; III=[-6.057454106 -4.070271408 -3.040378842 -2.422907504 -2.011571639 -1.688601017 -1.409863111 -1.219406958 -1.014356847 -0.868083316 -0.721893274 -0.590363981 -0.458884781 -0.312678041 -0.225364765]; w=2.*pi.*f(4); %f(4) can be change between f(1)....f(15) with length of f vector. #effective density edn= @(x)  rho0.*x(1).*(1+ ( (fi.*sigma./(j.*w.*rho0.*x(1))).*sqrt(1+ (j.*(4.*w.*rho0.*eta.*(x(1).^2))./(sigma.^2.*fi.^2.*x(2).^2))))); #effective bulk modulus ebm= @(x) (gamma.*P0)./ (gamma-((gamma-1).*(1+(8.*eta./(j.*w.*B.*(x(3).^2).*rho0)).*sqrt(1+(j.*(w.*B.*rho0.*(x(3).^2))./(16.*eta)))).^(-1))); #complex wave number kwave= @(x) (w.*sqrt(edn(x)./ebm(x))); #char impedance back_calc_2.m ZC=@(x) sqrt(edn(x).*ebm(x)); #general function x(1) tortuosity,x(2) viscous characteristic length,x(3) thermal characteristic length ZS=@(x) ((-j.*ZC(x).*cot(kwave(x).*L))./(fi.*rho0.*c)); optim=@(x) abs(RRR(4)+i.*III(4)-ZC(x)); ctl.XVmin = [1 0 0]; ctl.XVmax = [4 1 1]; # note to forumers: as a result of theory x(3)>x(2) but I can not define in ctl structure [x, obj_value, nfeval, convergence] = de_min (optim, ctl) -- Sent from: http://octave.1599824.n4.nabble.com/Octave-General-f1599825.html_______________________________________________ Help-octave mailing list Help-octave@gnu.org https://lists.gnu.org/mailman/listinfo/help-octave
Open this post in threaded view
|

## Re: Questions about de_min in octave

 EDIT Please forget previous one Sorry; I try to make a back calculation with using Johnson Champoux Allard mathematical model, which defines acoustic impedance behaviour of acoustic foams. f,RRR,III vectors are measured data(frequency,real and imaginer parts) from impedance tube (they are surface impedance), I try to obtain some critical parameters like tortousity,char. viscous and thermal length from this data with de_min function.   #back_calclation for porous samples clc clear all pkg load optim gamma=1.401 # specific heat ratio P0=99700 #pressure eta= 1.56E-5; #dynamic viscosity B=0.707 # Prandtl number fi=0.95 # porosity     L=34.35/1000 #thickness rho0=1.2 #air density sigma=8197# air resistivity c=340;# sound speed f=[202.53 300.94 399.35 502.52 599.34 704.10 800.92 897.74 1002.50 1100.91 1204.09 1305.67 1404.09 1500.92 1604.09]; RRR=[0.731942065 0.701451715 0.641506283 0.596238299 0.580492187 0.535207505 0.504733852 0.48898774 0.473158139 0.457395329 0.471037507 0.469968842 0.468933572 0.497370082 0.496284719]; III=[-6.057454106 -4.070271408 -3.040378842 -2.422907504 -2.011571639 -1.688601017 -1.409863111 -1.219406958 -1.014356847 -0.868083316 -0.721893274 -0.590363981 -0.458884781 -0.312678041 -0.225364765]; w=2.*pi.*f(4); %f(4) can be change between f(1)....f(15) with length of f vector. #effective density edn= @(x)  rho0.*x(1).*(1+ ( (fi.*sigma./(j.*w.*rho0.*x(1))).*sqrt(1+ (j.*(4.*w.*rho0.*eta.*(x(1).^2))./(sigma.^2.*fi.^2.*x(2).^2))))); #effective bulk modulus ebm= @(x) (gamma.*P0)./ (gamma-((gamma-1).*(1+(8.*eta./(j.*w.*B.*(x(3).^2).*rho0)).*sqrt(1+(j.*(w.*B.*rho0.*(x(3).^2))./(16.*eta)))).^(-1))); #complex wave number kwave= @(x) (w.*sqrt(edn(x)./ebm(x))); #char impedance back_calc_2.m ZC=@(x) sqrt(edn(x).*ebm(x)); #general function x(1) tortuosity,x(2) viscous characteristic length,x(3) thermal characteristic length ZS=@(x) ((-j.*ZC(x).*cot(kwave(x).*L))./(fi.*rho0.*c)); optim=@(x) abs(RRR(4)+i.*III(4)-ZC(x)); ctl.XVmin = [1 0 0]; ctl.XVmax = [4 1 1]; # note to forumers: as a result of theory x(3)>x(2) but I can not define in ctl structure [x, obj_value, nfeval, convergence] = de_min (optim, ctl) -- Sent from: http://octave.1599824.n4.nabble.com/Octave-General-f1599825.html_______________________________________________ Help-octave mailing list [hidden email] https://lists.gnu.org/mailman/listinfo/help-octave-- Sent from: http://octave.1599824.n4.nabble.com/Octave-General-f1599825.html_______________________________________________ Help-octave mailing list [hidden email] https://lists.gnu.org/mailman/listinfo/help-octave