The initial ultimate bod after mixing of the bergelmir river is 12.0 mg · l−1. the do in the bergelmir river after the wastewater and river have mixed is at saturation. the river temperature is 10◦ c. at 10◦ c, the deoxygenation rate constant (kd) is 0.30 day−1 , and the reaeration rate constant (kr) is 0.40 day−1 . determine the critical point (tc) and the critical do. tc = 2.88 days. critical do = 7.53 mg · l−1

Fluids at rest possess no flow energy. a)- true b)- false

Different types of steels contain different elements that alter the characteristics of the steel. for each of the following elements, explain what the element does when alloyed with steel.

Ajournal bearing has a journal diameter of 3.250 in with a unilateral tolerance of 20.003 in. the bushing bore has a diameter of 3.256 in and a unilateral tolerance of 0.004 in. the bushing is 2.8 in long and supports a 700-lbf load. the journal speed is 900 rev/min. find the minimum oil film thickness and the maximum film pressure for both sae 20 and sae 20w-30 lubricants, for the tightest assembly if the operating film temperature is 160°f. a computer code is appropriate for solving this problem.