Flow Characteristics and Sizing of Annular Seat Valves for Digital Displacement Machines

This paper investigates the steady-state flow characteristics and power losses of annular seat valves for digital displacement machines. Annular seat valves are promising candidates for active check-valves used in digital displacement fluid power machinery which excels in efficiency in a broad operating range. To achieve high machine efficiency, the valve flow losses and the required electrical power needed for valve switching should be low. The annular valve plunger geometry, of a valve prototype developed for digital displacement machines, is parametrized by three parameters: stroke length, seat radius and seat width. The steady-state flow characteristics are analyzed using static axi-symmetric computational fluid dynamics. The pressure drops and flow forces are mapped in the valve design space for several different flow rates. The simulated results are compared against measurements using a valve prototype. Using the simulated maps to estimate the flow power losses and a simple generic model to estimate the electric power losses, both during digital displacement operation, optimal designs of annular seat valves, with respect to valve power losses, are derived under several different operating conditions

Violence against radiologists. II: psychosocial factors

PURPOSE: Violence against radiologists is a growing problem. This study evaluated the psychosocial factors associated with this phenomenon. MATERIALS AND METHODS: A questionnaire was administered to 992 Italian radiologists. RESULTS: Physical violence experienced in the previous 12-month period was associated with the radiologist's poor mental health [odds ratio (OR) 1.11] and overcommitment to work (OR 1.06), whereas radiologists in good physical health (OR 0.64), with job satisfaction (OR 0.96) and with overall happiness (OR 0.67) were less exposed. Nonphysical abuse was equally associated with the radiologist's poor mental health (OR 1.10) and overcommitment (OR 1.14) and negatively associated with physical health (OR 0.54), job satisfaction (OR 0.96), happiness (OR 0.81), organisational justice (OR 0.94) and social support (OR 0.80). CONCLUSIONS: Preventive intervention against violence in the workplace should improve workplace organisation and relationships between workers