2147
Simulation models are still to be implemented and validated mostly because the design of heterogeneous compositional gradients are very complex .
 enabling technology: Simulation; material: be; engineering feature: design; concept or principle: heterogeneous
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:
 enabling technology: Simulation; material: be; engineering feature: design; concept or principle: heterogeneous