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The research shows that the integrity of the samples ( in terms of density as well as metallurgy ) varies dramatically in the two investigated materials due to the different conditions that are required to melt the interface of the stacked droplets .
 research, integrity, samples, density, as, as, materials, melt, interface, droplets
Please list all entity words in the text that fit the category. Output format is "word1, 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:
 research, integrity, samples, density, as, as, materials, melt, interface, droplets