MATLAB dsolve not working -

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i'm solving diffusion equation in matlab particular system, there problem second solution get, nsub(r). ideally want function of r 2 undetermined constants , while first part of expression indeed besselfunctions contains ,r, 'ignoreanalyticconstraints', true). know how solve problem , goes wrong? here code:

clear clc  %%%%%% constants %%%%%%% r_nw=50*10^(-9); pitch_nw=500*10^(-9); f_sub=10^18; f_nw=10^18; l_nw=100*10^(-6);  %%%%%% diffusion on wire %%%%% tau_nw=1000*10^(-9); d_nw=1*10^-9; lambda_nw=sqrt(d_nw*tau_nw);  %%%%%% diffusion on substrate %%%%%%% tau_sub=100*10^(-9); d_sub=1*10^(-9); lambda_sub=sqrt(d_sub*tau_sub);  %%%%%% diffusion equation on wire %%%%%%%% syms nw(z) nw = dsolve(d_nw*diff(nw,z,2) == -f_nw + nw/tau_nw,nw(l_nw)==0); nw(z)=simplify(nw); dnw = diff(nw,z);  %%%%%% diffusion equation on substrate %%%%%% syms nsub(r) nsub = dsolve(diff(nsub,r,2)+1/r*diff(nsub,r) == -f_sub + nsub/tau_sub); dnsub = diff(nsub,r);


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