Coupled Extensional-Torsional Vibration Frequency of Hoisting Rope in Tower-Type Friction Drive Hoist System
In order to avoid resonance, and to enhance safety of hoisting system and monitoring reliability, an impact mechanical model of mine hoisting rope for friction drive hoist system was built. According to Hamilton principle and considering the effect of oriented pulley and hoisting rope string, coupled extensional-torsional and extensional only mathematical models of hoisting rope were deduced. Mode shape and transcendental equation of angular frequency were obtained based on the hypothesis that the wave of vibration propagated with sine shape. With numerical calculation, results show that the frequency considering the effect of oriented pulley and hoisting rope string was slightly lower comparing with the frequency ignoring the effect at the bottom of shaft, but much different at the mouth; and there is significant difference between coupled frequency and extensional vibration only. Thereby, to make the design and monitoring of mine hoisting much more reliably, it is suggested that the extensional-torsional coupled vibration of hoisting rope, oriented pulley and hoisting rope string should be considered.
Modeling and Natural Frequency Characteristics of Coupled Vibration with Varying Length of Hoisting Rope in Drum Winding System
In order to avoid resonance and enhance safety during designing hoist control method for mine hoisting system, the model of drum winding system guided by a head heave with varying length of hosting rope was established by the method of moving frame approach. According to Hamilton principle, the extensional, torsional and lateral coupled mathematical model with the effect of a concentrated mass was described to investigate the natural frequency characteristics. The mode shape and transcendental equation of angular frequency were obtained by supposing that the wave of vibration propagated with sine shape and using characteristic of the Heaviside function. By taking the scanning method of frequency and the hypothesis of transient, all vibration frequencies of the transcendental equation during drum winding could be calculated numerically, and frequencies at the bottom of shaft during the drum winding were given as a calculation example.
Air scrubbing techniques for ammonia and odor reduction at livestock operations : review of on-farm research in the Netherlands
Acid scrubbers and biotrickling filters have been developed for ammonia (NH3) removal at pig and poultry houses 
in The Netherlands over the last 20 years to prevent acidification and eutrophication of soils. Because of growing 
suburbanization, odor removal is increasingly considered important as well. In this review, we report the results of the on-farm 
research on full-scale operated scrubbers for treatment of exhaust air from animal houses with regard to NH3 and odor 
removal in The Netherlands. The NH3 removal of acid scrubbers ranged from 40% to 100% with an overall average of 96%. 
The NH3 removal of biotrickling filters ranged from -8% to +100% with an overall average of 70%. Minimum empty bed air 
residence times (EBRTs) were 0.4 to 1.1 s. For acid scrubbers, process control with pH measurement and automatic water 
discharge is sufficient to guarantee sufficient NH3 removal. For biotrickling filters, however, improvement of process control 
is necessary to guarantee sufficient NH3 removal. The odor removal of acid scrubbers ranged from 3% to 51% with an overall 
average of 27%. The odor removal of biotrickling filters ranged from -29% to +87% with an overall average of 51%. 
Minimum EBRTs were 0.5 to 2.3 s. Further research is necessary to explain this variation and to improve the odor removal 
efficiency of both acid scrubbers and biotrickling filters.