i do have 2 graphics but I need to find the opposite of their sides

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sevgul demir 2022-11-22

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https://ww2.mathworks.cn/matlabcentral/answers/1858898-i-do-have-2-graphics-but-i-need-to-find-the-opposite-of-their-sides

评论： Image Analyst 2022-11-22

i do have 2 graphics but I need to find the opposite of their sides

% Inputs
R = 8.314; % Ideal gas constant (J/molK)
F = 96487; % Faraday’s constant (Coulombs)
Tc = 80; % Temperature in degrees C
P_H2 = 3; % Hydrogen pressure in atm
P_air = 3; % Air pressure in atm
A_cell=100; % Area of cell
N_cells=90; % Number of Cells
r = 0.19; % Internal Resistance (Ohm-cm^2)
Alpha = 0.5; % Transfer coeffi cient
Alpha1 = 0.085; % Amplifi cation constant
io = 10^-6.912; % Exchange Current Density (A/cm^2)
il = 1.4; % Limiting current density (A/cm2)
Gf_liq = - 228170; % Gibbs function in liquid form (J/mol)
k = 1.1; % Constant k used in mass transport
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Convert degrees C to K
Tk = Tc + 273.15;
% Create loop for current
loop = 1;
i = 0;
for N = 0:150;
    i = i + 0.01;
    % Calculation of Partial Pressures
    % Calculation of saturation pressure of water
    x = -2.1794 + 0.02953 .* Tc-9.1837 .* (10.^-5) .* (Tc.^2) + 1.4454 .* (10.^-7) .* (Tc.^3);
    P_H2O = (10.^x);
    % Calculation of partial pressure of hydrogen
    pp_H2 = 0.5 .* ((P_H2)./(exp(1.653 .* i./(Tk.^1.334)))-P_H2O);
    % Calculation of partial pressure of oxygen
    pp_O2 = (P_air./exp(4.192 .* i/(Tk.^1.334)))-P_H2O;
    % Activation Losses
    b = R .* Tk./(2 .* Alpha .* F);
    V_act = -b .* log10(i./io); % Tafel equation
    % Ohmic Losses
    V_ohmic = -(i .* r);
    % Mass Transport Losses
    term = (1-(i./il));
    if term > 0;
        V_conc = Alpha1 .* (i.^k) .* log(1-(i./il));
    else
        V_conc = 0;
    end
    % Calculation of Nernst voltage
    E_nernst = -Gf_liq./(2 .* F) - ((R .* Tk) .* log(P_H2O./(pp_H2 .* (pp_O2.^0.5))))./(2 .*F);
    % Calculation of output voltage
    V_out = E_nernst + V_ohmic + V_act + V_conc;
    if term < 0;
        V_conc = 0;
        break
    end
    if V_out < 0;
        V_out = 0;
        break
    end
    figure(1)
    title('Fuel cell polarization curve');
    xlabel('Current density (A/cm^2)');
    ylabel('Output voltage (Volts)');
    plot(i,V_out,'o')
    grid on
    hold on
    disp(V_out);
    % Calculation of power
    P_out = N_cells .* V_out .* i .* A_cell;
    figure(2)
    title('Fuel cell power');
    xlabel('Current density (A/cm^2)');
    ylabel('Power(Watts)');
    plot(i,P_out,'o');
    grid on
    hold on
    disp(P_out);
end

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sevgul demir 2022-11-22

i know what my codes makes :) for examle for the first one its starting from the 1.1and going down if i want to make it start from 0 and going up what should i do? thats the question

Image Analyst 2022-11-22

在 MATLAB Online 中打开

Yes but you forgot to post the screenshots so no one else who might be able to help you knows what they look like so I thought I'd help out and show them. Otherwise people may simply move on to a different question.

To flip it, you have to change the equation. So when you get V_out, subtract it from the first element:

V_out = V_out(1) - V_out;

and then plot it:

plot(i,V_out,'o')

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