Human behavior in a staircase during a total evacuation drill in a high‐rise building

Many studies have been conducted on the evacuation behavior on the staircases of buildings, but very little data are available for a situation with many occupants in a crowded high‐rise building. Therefore, this study investigated the evacuation behavior of a large number of evacuees on the staircase of a 25‐story high‐rise building. A total evacuation drill was conducted with 2088 evacuees, and the behavior of 1136 evacuees on the landings of the south staircase was recorded by a video recorder on the ceiling. The relationship between the density and speed of the evacuees on the landings was analyzed from the evacuation data for two situations: without and with merging in the stair flow. The evacuation stair flow in this drill had merging occupants entering from the floors, but no one entered from the lower floors during the latter period of the drill. Therefore, the flow during the latter period was treated as non‐merging flow, for which it was observed that, when the staircase was fully crowded, the density on the landings in the moving situation was different from that in the stopped situation. Moreover, the density on the landings was different from that on the treads. Furthermore, in the merging flow, a merging ratio of approximately 50:50 occurred during the congested evacuation. Copyright © 2016 John Wiley & Sons, Ltd.     

Breakup dynamics for high‐viscosity droplet formation in a flow‐focusing device: Symmetrical and asymmetrical ruptures

The breakup mechanism of high‐viscosity thread for droplet formation in a flow‐focusing device is investigated using a high‐speed digital camera. Aqueous solution of 89.5%‐glycerol is used as the dispersed phase, while silicone oil as the continuous phase. The breakup process of the dispersed thread presents two categories: symmetrical rupture and asymmetrical rupture. Furthermore, the rupture behavior could be divided into two stages: the squeezing stage controlled by the squeezing pressure and the pinch‐off stage controlled by viscous stresses of both phases and surface tension. Specifically, it suggests that the differences in the shape of the liquid–liquid interface and the dynamics in the two breakup processes are caused by the disparity of the strain field at the point of detachment. Moreover, the thinning rate and the dynamics of the dispersed thread change with the viscosity of the continuous phase, but are less dependent of the flow rate of the continuous phase. © 2015 American Institute of Chemical Engineers AIChE J, 62: 325–337, 2016     

The ablative behavior of high linear chains and its role in the thermal stability of polyethylene: a combined P‐TREF−TGA study

Ethylene copolymers contain short chain branches (SCBs) which have great influence on their properties. An ethylene/1‐hexene copolymer distinguished in terms of the number of butyl SCBs was precisely separated based on differences in crystallizability using the preparative temperature‐rising elution fractionation (P‐TREF) method and was then studied via TGA and DSC. A comparison between the results obtained and the literature suggested a short chain branch distribution (SCBD) functionality for a included in the general linear form T_m (°C) = ?a(SCBD) × (SCB) + b. P‐TREF?TGA results showed that the highly linear chains acted as ablative layers which could increase the thermal stability and durability of polyethylene in the absence of any mineral additive. Furthermore, the P‐TREF?TGA data displayed an interesting interrelationship between temperature at maximum rate of degradation (T_max) and the number of butyl SCBs over all the heating rates (10, 25, 50 and 100 °C min^‐1). The role of the number of butyl SCBs in thermal degradation was exhausted by higher heating rates, whereas the ablation capability was enhanced. Kinetic studies demonstrated that the activation energy dropped on increase in butyl branch content within the backbone. © 2015 Society of Chemical Industry