if the normal stresses at point a and b on the section of a bending beam with rectangular section are σa = 20mpa and σb = 10mpa,then the normal stress at point d in the middle of ab is( )
in the process of transforming an innovative competition plan from an idea into a real thing, new ideas will be generated, optimized and sublimated.
“why not buy it? it only cost you as much as a book ____.”
design patents focus on the ( ) creations made by designers on the appearance of a product.
the capacity of a member to maintain its original equilibrium state under external load is the .
in ( ), the first china college students “internet ” innovation and entrepreneurship competition is hosted
for college students to start a business, if they want to build a successful product, development is only the first step, and product promotion is a more important step.