9223
Nano-indentation measurements revealed that shot-peening caused surface hardening , with the hardness profile from the surface to the interior of the bulk disappearing 50 μm below the surface .
 manufacturing process: surface hardening; machanical property: hardness; concept or principle: surface; concept or principle: surface
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
 Entities: surface hardening, hardness, surface, surface 
Answer:
 manufacturing process: surface hardening; machanical property: hardness; concept or principle: surface; concept or principle: surface