Traffic flow in cities is increasing rapidly as cities modernize. The problem of parking is getting worse and worse due to insufficient parking lots in large cities, and people are paying more attention to safety issues in buildings due to the development of underground parking floors. There are new problems for fire safety because a building's functions and materials, structural type, size, and supporting facilities are very different between the traditional buildings and buildings with underground parking floors. When a fire occurs in an enclosed underground parking floor, it is hard for people to evacuate due to incomplete combustion producing heavy smoke. In this work, we use the Fire Dynamic Simulator (FDS) to study the effect of a mechanical smoke ventilation system to retard the development of a smoke layer. The simulated results indicate that, although the installation of a mechanical smoke ventilation system would retard the deposition of a smoke layer, fresh air also drawn in increases the heat release rate of a car fire. Most importantly, a mechanical smoke ventilation system can extend the escape time for people during the initial stages of a fire.

Polyvinylidene fluoride (PVDF) piezoelectric nanofibers were fabricated through near-field electrospinning (NFES) to develop a flexible piezoelectric element. Innovative screen printing technology was employed to produce bend-type electrodes designed with d 33 mode patterns. The electrodes and PVDF nanofibers were then attached to a polyimide film substrate. Compared with piezoelectric ceramics, piezoelectric fibers are inexpensive, flexible, and highly biocompatible. They also have a higher electron density than piezoelectric films, indicating that they are more efficient in electromechanical conversion. Thus, in this study, we adopted piezoelectric fibers to create a displacement sensor with bend-type electrodes that employed optimized pattern designs to increase the efficiency of piezoelectric conversion and sensitivity. The experimental results revealed that the type of electrode was critical for enhancing output voltage. The novel bend-type electrodes induced an average positive voltage of 960.5 mV during a tapping experiment, increasing the maximum voltage by 59.74% compared with a series-type electrode. The positioning accuracy of the displacement sensor was 600 μm; thus, the sensor could successfully determine positioning, confirming the feasibility of the displacement sensing mechanism.