function [ output_args ] = make_bck_twin( totaltime)

outfile='obs_float/vel_bck_all.dat';
format long
ufile='obs_float/uzero.dat';
vfile='obs_float/vzero.dat';
 fid=fopen(outfile,'w');

for i=1:totaltime
    
    
    time_step=i;
ubck=load(ufile);
vbck=load(vfile);

  
 vel_bck=zeros(size(ubck,1),5);

 vel_bck(:,1)=time_step;
 vel_bck(:,2)=ubck(:,2);
 vel_bck(:,3)=ubck(:,3);
 vel_bck(:,4)=ubck(:,4);
 vel_bck(:,5)=vbck(:,4);



 fprintf(fid,'%d %d %d %f %f\n',vel_bck');

 

end

 fclose(fid);
end