Electronic control hydraulic impactor based on pressure feedback
The impact energy of the traditional hydraulic impactor can be regulated manually between the second and the third grade, and its impact frequency can not be adjusted independently. Also, they have to stop working for adjustment. In order to alter this situation, a new hydraulic impactor DBS500, which controlled by micro-electronic system, has been designed and its functions are showed as following: The impact energy can reach 500 joules and its impact frequency also realizes regulation from 0 to 8Hz steplessly. It can estimate the work object's nature by piston's rebound behavior. It can self-regulate the impact energy and frequency according to the object's nature, so that can improve the working efficiency and adapt the power of the loader.
MICROCOMPUTER SIMULATION OF PERCUSSIVE DRILLING
Churn drilling, down-the-hole drilling, hammer drilling, and related drilling and breaking processes are simulated by means of a microcomputer. The simulation programs are written in Apple Pascal f ...
Fieldwork in geography teaching: A critical review of the literature and approaches
Abstract Virtually all lecturers in geography recognise the importance of fieldwork as a vital mode of teaching in the subject. This paper draws on material produced as part of a HEFCE review of teaching and learning in the field and assesses the implications of recent changes in higher education for field studies in geography. The literature on the development of, and recent changes in, fieldwork practice is reviewed and assumptions about appropriate forms of teaching and assessment are challenged. The need for carefully integrated preparation of project‐orientated fieldwork is stressed and the importance of debriefing and feedback after field visits is emphasised. Various suggestions for guidelines on good practice are presented. Finally, a range of future issues and problems in fieldwork is identified and discussed.