Design of special truss moment frames considering progressive collapse

In this study the progressive collapse resisting capacity of the Special Truss Moment Frames (STMF) was investigated. To this end STMF with various span lengths, numbers of story, and lengths of special segment were designed. Their performances against progressive collapse were evaluated based on arbitrary column removal scenario. It was observed that all the model structures designed per the AISC Seismic Provision collapsed as a result of plastic hinge formation at special segment when a column was suddenly removed. A design procedure was developed based on the energy balance concept to prevent progressive collapse. The model structures redesigned using the developed design procedure turned out to remain stable after a column was suddenly removed and satisfy the acceptance criteria of the GSA guidelines.     

A highly sensitive chemical gas detecting transistor based on highly crystalline CVD-grown MoSe<Subscript>2</Subscript> films

Layered semiconductors with atomic thicknesses are becoming increasingly important as active elements in high-performance electronic devices owing to their high carrier mobilities,large surface-to-volume ratios,and rapid electrical responses to their surrounding environments.Here,we report the first implementation of a highly sensitive chemical-vapor-deposition-grown multilayer MoSe2 field-effect transistor (FET) in a NO2 gas sensor.This sensor exhibited ultra-high sensitivity (S =ca.1,907 for NO2 at 300 ppm),real-time response,and rapid on-off switching.The high sensitivity of our MoSe2 gas sensor is attributed to changes in the gap states near the valence band induced by the NO2 gas absorbed in the MoSe2,which leads to a significant increase in hole current in the off-state regime.Device modeling and quantum transport simulations revealed that the variation of gap states with NO2 concentration is the key mechanism in a MoSe2 FET-based NO2 gas sensor.This comprehensive study,which addresses material growth,device fabrication,characterization,and device simulations,not only indicates the utility of MoSe2 FETs for high-performance chemical sensors,but also establishes a fundamental understanding of how surface chemistry influences carrier transport in layered semiconductor devices.