function kval = Kr(u,v)

nu = size(u,1);
nv = size(v,1);

norm_u = sqrt(sum(u.^2,2));
norm_v = sqrt(sum(v.^2,2));

k1 = K1(u,v);

kval = exp(-0.5*(repmat(norm_u.^2,1,nv)-2*k1+repmat(norm_v'.^2,nu,1)));

