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Due to the optimization of process parameters , the density of volumetric specimens above 99 % was reached and vaporization losses of the alloying elements were significantly reduced , but solidification cracks could not be eliminated .
 optimization, process parameters, density, alloying elements, solidification cracks, be
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:
 optimization, process parameters, density, alloying elements, solidification cracks, be