Top-down effects of predators in systems depend on the rate at which predators consume prey, and on predator preferences among available prey. In invaded communities, these parameters might be difficult to predict because ecological relationships are typically evolutionarily novel. We examined feeding rates and preferences of a crab native to the Pacific Northwest, Cancer productus, among four ...

This paper presents a novel pneumatic Down-The-Hole (DTH) hammer with self-rotation bit used for rock drilling, and the mechanical structure working principle are mainly covered. A unique mechanism ratchet pawl incorporated in DTH is proposed percussion-rotation drilling to break rock. The drill can rotate while pipe stays still because of design reduces friction between borehole. Firstly, rati...

OBJECTIVES Prolonged exposure to severe chipping hammer vibration may cause hand-arm vibration syndrome. A reliable test method is required to select appropriate tools and assist in the development of better chipping hammers. In the present study, the ISO standardized test method (ISO 8662-2, 1992) was examined through an investigation of the vibration characteristics of chipping hammers operat...

The vibrations generated by manual machines can cause occupational diseases with both vascular and osteoarticular affectations, also known as hand-arm vibration syndrome. pneumatic rotary hammer is one of these machines, widely used in the construction sector. In bibliography consulted, it found that transmission from handle to system depends on composition material design handle. Although ther...

The article considers the issues of need to improve quality technological process sowing seeds row crops with precision seeding drills and main trends their improvement from point view possibility introducing seed lines control systems for processes into design a serial drill, also presents new apparatus an automated system monitoring controlling cultures, scheme advantages using are developed ...