There are several types of analyses that interest engineers, all of which involve mathematical modeling. Structural analysis deals with linear and nonlinear models and stresses on a material. The linear models assume the material does not plastically deform (the remaining deformation after the load causing it is removed); nonlinear models stress the material past its elastic capabilities. The stresses in the material then vary with the amount of deformation. Vibrational analysis deals with possible resonance and subsequent failure. It is used to test a material that may experience random vibrations, impacts, or shocks. Fatigue analysis is used to determine the life of a material or structure. It shows the effects of occasional (periodic) or cyclic loading on a structure or object, pointing out where cracks or fractures are most likely to occur. Engineers measure heat transfer to determine a material or structure’s conductivity or thermal fluid dynamics. In this way, researchers understand how a material will respond to various hot and cold conditions—or even how it diffuses heat and cold—over time.