Array Valued Integral Problem - Tikhonov Regularization

I am working on a script to perform Tikhonov Regularization on experimental data. I need to first set up an operator matrix K (this is the problem) that transforms the desired solution f (a vector) into the experimental data b (also a vector), ie, Kf=b. In other words, I aim to solve a Fredholm Integral equation of the first kind using the Tikhonov method.

K depends on two parameters, r (distance) and t (time). At each r and t, the integral along z should return a scalar to populate that element in the array.

I am encountering this error message: Warning: Reached the limit on the maximum number of intervals in use. Approximate bound on error is 1.5e-01. The integral may not exist, or it may be difficult to approximate numerically to the requested accuracy.

The relevant code:

b_magn = 9.27400968E-24; %bohr magneton (J/T)
gamma_e = 1.760859708E11; %gyromagnetic ratio of electron (rad/(s*T))
planck = 6.62606957E-34; %planck's constant (J*s)
hbar = planck/(2*pi); %planck's reduced constant

r = [1 : .01 : 11]; %nm 
t = [0 : .01 : 10]; %us

omega_d = gamma_e^2*hbar./(r*1e-9).^3;
for it = 1:numel(t);
    for ir = 1:numel(r);
      y = @(z) cos((1-3.*z.^2)*(t(it)*1e-6).*omega_d(ir));
      K = integral(y,0,1,'Arrayvalued',true); %operator matrix
    end
end

[U,S,V] = svd(K);

The function y and the bounds of integration seem innocuous enough. I do not know where I am running into issue.

Thanks!