Sharif Digital Repository

Designing of an efficient emergency ventilation system is one of the main approaches to prevent the perilous fire in tunnel phenomenon. For this purpose, firstly, fire behavior and its heat release rate should be investigated. Knowing about temperature distribution and smoke movement is the second step. One of the most considerable factors in smoke control is critical velocity. It means the minimum velocity to prevent backlayering flow. If longitudinal ventilation velocity were less than this amount, smoke and hot gases originated from the fire can enter the upstream zone. This may cause lack of oxygen and decrease visibility for the passengers when they are escaping from the fire field. In... 

Polypropylene block copolymer is used in different industries like pipe productions. This copolymer has proper mechanical properties, specially it has good impact strength, but in some applications it’s elastic modulus (stiffness) is not enough and that leads to some problemes in servise. Nucleating agents influence crystalline structure and properties and also the mechanical properties by controlling the crystallization process. Nanoparticles also have a beneficial effects on physical and mechanical properties. In this study, the effect of adding two types of α-phase nucleating agents (commercial names NA11 and DMDBS) in the form of masterbatch wt 5% with a carrier of polypropylene block...