Vim tias cov pwm sib txawv tuag tau siv nyob rau ntau qhov chaw, thiab kev tsim tshuab kev lag luam ntawm cov kws tshaj lij kev lag luam kuj tau dhau los ntawm qee qhov kev hloov pauv thiab kev tsim tawm hauv cov xyoo no, hauv qhov no, cov qauv kev cai dav dav ntawm lub tshuab nqus dej tuag yog sau ua ke.