Why might the perimeter formwork be set below grade?

Air inially occupying a volume of 1 m2 at 100 kpa, 27 c undergoes three internally reversible processes in series. process 1-2 compression to 500 kpa during which pv constant process 2-3 adiabatic expanslon to 100 kpa process 3-1: constant-pressure expansion to 100 kpa (a) calculate the change of entropy for each of the three processes. (b) calculate the heat and work involved in each process. (c) is this cycle a power cycle or refrigeration cycle?

Plot schematically the tensile stress versus strain curves for a typical thermoplastic material at a temperature below its glass transition temperature (tg and at a temperature above its tg, respectively. do the same for a typical thermosetting material. list in a table any differences or similarities between the two materials at t> tg and t < tg, respectively, and relate them to the structures of the two types of polymers

Steam enters a converging-diverging nozzle at 1.0 mpa and 500°c with a negligible velocity at a mass flow rate of 2.5 kg/s, and it exits at a pressure of 200 kpa. assuming the flow through the nozzle to be isentropic, determine: the exit area and (a) (b) the exit mach number