Provided is a flow rate measuring apparatus which prevents a reduction in flow-rate detection accuracy through reducing stress applied to a flow rate detection element. The electron column having an electron emission source and a lens unit according to the present invention is characterized in that the lens unit includes two or more lens layers and performs both a source lens function and a focusing function. The second controller is configured to provide discrete supply chain control and optimization for the process facility and to track at least one of demand requirements and shipping requirements for product manufactured by a discrete supply chain manufacturing process.