In the last few years, vegetable industry developed rapidly in Hebei province, intensive raising seedling as its main component, also entered a period of rapid development. The background and characteristics, the current situation and existed questions of intensive seedling cultivation were...

We introduce the stratified sampling method, and put forward theoretical unbiased estimation of stratified sampling program, as well as the model and statistics of experimental design test. We also discuss the establishment of dietary exposure model, pollutant distribution model, and risk...