1914
It is already well known that variation of process parameters may influence the formation of porosity and may lead to extensive flaws and build imperfections , as is shown for example in a round robin test recently .
 concept or principle: variation; concept or principle: process parameters; machanical property: porosity; material: lead; concept or principle: flaws; process parameter: build; material: as; process characterization: round robin test
Please list all entity words in the text that fit the category.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} 
Answer:
 concept or principle: variation; concept or principle: process parameters; machanical property: porosity; material: lead; concept or principle: flaws; process parameter: build; material: as; process characterization: round robin test