fundamental understanding of the goaf gas distribution in a gassy coal mine is necessary for developing effective goaf gas drainage strategies in the longwall coal mine. the goaf gas was subjected to the surface and body forces that were classified depending upon whether they acted on the surface area or the volume of the gas element. of these forces, the body forces were more predominant in di...

The California Department of Health Services' Occupational Health Branch and others have identified the construction industry as being at high risk for injuries, illnesses, and fatalities. Effective tailgate trainings (brief job site safety meetings) can be a powerful tool to promote hazard awareness and safe work practices. The authors found that many contractors and supervisors conducted inef...

In this paper, we present the design and implementation of a wireless sensor based piggybacking and tailgating detection system to detect unauthorized attempt to gain access to a secured area. A set of Sun SPOT wireless sensor platform is adopted for acceleration sensor, transmitter, and receiver units for the system. A wireless sensor embedded in a security door collects the signal of door mov...

Fundamental understanding of the goaf gas distribution in a gassy coal mine is necessary for developing effective goaf gas drainage strategies in the longwall coal mine. The goaf gas was subjected to the surface and body forces that were classified depending upon whether they acted on the surface area or the volume of the gas element. Of these forces, the body forces were more predominant in di...

In the process of working face mining, permeability coal seam and crack evolution characteristics overlying strata are very important for efficient gas drainage. this study, distribution stress field in their relations analyzed mainly by 3DEC numerical simulation. Furthermore, combined with on-site measurement stress, pressure, seepage front before after coupling effect law migration deeply exp...