Write a three paragraphs to summarize current efforts and challenges aimed at producing green concrete. (150 words minimum)

List two methods that are used in heat exchanger design and analysis.

(Q2) As a fire engineer, assume that you are assigned to a fire engineering design of the retail building with extraordinary atrium that connected six floors. You have to adopt fire engineering approach on this project and conduct a theoretical analysis of full evacuation in this commercial building. Please brief your design procedures. (Hint: Relationship between occupant density, travel speed and flow is recommended to consider.)

What are the latest technologies to remove sulfate from industrial wastewater?

A stream of carbon dioxide flows at a rate of 15.0 kmol/h. Use the truncated-viralequation-of-state to find the volume flow-rate at 60.0 atm and 70.0 oC.

A stream of carbon dioxide flows at a rate of 15.0 kmol/h. Use the truncated-viralequation-of-state to find the volume flow-rate at 60.0 atm and 70.0 oC.

The counts per second (cps) changes when the spot size is changed. Why?

The counts per second (cps) also changes when kV is changed. Why?

In general, which parameter would you change, spot size or kV, to increase the counts per second? Why?

This is when using an Scanning Electron Microscopy (SEM) or Energy Dispersive Spectroscopy (EDS).

Two kilograms of CO₂ gas is contained in a piston-cylinder assembly at a pressure of 6.5 bar and a temperature of 300 K. The piston has a mass of 5000 kg and surface area of 1m². The friction of the piston on the walls is significant and cannot be ignored. The atmospheric pressure is 1.01325 bar. The latch holding the piston in position is suddenly removed and the gas is allowed to expand. The expansion is arrested when the volume is double the original volume. Determine the work appearing in the surroundings. Will it be the same as the work done by the gas?

PROBLEM: Ammonia is used as a refrigerant. It is compressed outdoors, and the ammonia is then liquefied and circulated through the refrigerator's evaporator heat exchanger. The evaporator is indoors. The room containing the evaporator has a net open volume of 1000 m3 and a ventilation rate equal to two air changes per hour. A leak develops in an ammonia line that results in 50 g of ammonia being released per minute. 1. How long will it take for the ammonia concentration to increase to the PEL concentration? 2. How long will it take to reach the IDLH concentration? 3. If the flow of ammonia is stopped at the time the IDLH concentration is reached, how long will it be before the concentration is reduced to the PEL concentration? You may assume that the mixtures of gases are ideal at the low pressures involved. Also assume that the ammonia is mixed with the air in the room completely and instantaneously and that the air- ammonia mixture leaving the room has the same concentration as the mixture in the room. Hint: Use a differential equation and separation of variables to solve.

4 (a) Derive a relation for the oxygen pressure dependence of electrical conductivity in NiO.
(b) Discuss the effects of Cr2O3 additions on the electrical conductivity of NiO, giving equations describing the temperature at which the conductivity changes from intrinsic to extrinsic in relation to the impurity concentration.