Papers by Author: Zhi Gang Song

Abstract: Exposure to biogenic aerosols such as airborne bacterium has hazardous effects upon human health. Mycobacterium tuberculosis (MTB) bacteria is a highly pathogenic microbe and arises large challenges to the enclosed laboratories for biosafety and the health of people working in them. Number concentration and size spectra of indoor aerosols were examined in the Animal Biosafety Level 3 (ABSL-3) laboratory located in Shanghai’s south suburb in July 2010. Mean particle concentration at center of the core room in dissecting experiment to MTB infected mouse (200 cm^-3) was equivalent to feeding experiment to MTB infected mouse (200 cm^-3), and roughly 2 times higher than background (91 cm^-3). Mean particle size distribution at center of the core room exhibited a bi-peak feature under dissecting and feeding conditions, but a mono-peak feature under background condition. Because of dual negative air pressure and high frequency cleaning, MTB bacteria emitted from infected agents did not appear in the air of the preparation and core rooms. Airborne particle sampling demonstrated that MTB aerosol contamination was not detected in the indoor air. This result indicates that online monitoring for particle microphysical properties is one valuable approach to early warn and protect the safety of ABSL-3 laboratories.

Abstract: Abstract. Lateral pedestrian loads and flexible footbridge form a dynamic interaction system, which has a special lock-in phenomenon and results the instability of the dynamic system when the pedestrian number reaches certain critical value. A simplified theoretical equation to model the dynamic interaction system and to estimate critical pedestrian number is proposed. The lateral pedestrian loads resulted by structural vibration is first analyzed from a view point of social force model. And then, combined with structural vibration equation, the control differential equation for describing the dynamic interaction system is proposed. The control equation explains why the lock-in phenomenon is resulted and how to estimate the critical pedestrian number. Two typical footbridges are investigated and the results show that critical pedestrian number estimated by the model is more close to those by field observation.