with speed increasing in high-speed trains, due to limitations of other types of brakes, aerodynamic brake has become an important braking method. in this task to make better use of brake’s panel different configurations are examined and the best panel shape which provides the reasonable drag coefficient is introduced. the results of simulations are carried out with the computational fluid dyna...

experimental work was carried out to investigate the influence of impeller speed, granulation time, binder mass and their interactions on granule size distribution, mean size and binder content distribution in a conical high shear granulator. it was observed that the response of high shear granulation to changes in process parameters varies significantly from one operating condition to another....

in the present study a quasi 2-d numerical model is developed for calculating air concentration distribution in rapid flows. the model solves air continuity equation (convection diffusion equation) in the whole flow domain. this solution is then coupled with calculations of the free surface in which air content in the flow is also considered. to verify the model, its results are compared with a...

PURPOSE The aim of this study was to compare the microleakage of unfilled and filled sealants after conventional, bur, and air-abrasion tooth preparation. METHODS Seventy-two extracted molars were randomly divided into three groups. In group 1, 24 teeth were prepared by pumicing and acid etching with 37% phosphoric acid. In group 2, 24 teeth were prepared with a 1/4-round bur in a low-speed h...

scaling challenges and limitations of conventional silicon transistors have led the designers to apply novel nano-technologies. one of the most promising and possible nano-technologies is cnt (carbon nanotube) based transistors. cnfet have emerged as the more practicable and promising alternative device compared to the other nanotechnologies.  this technology has higher efficiency compared to t...

Background Improper storage of the electrosurgical handpiece has been identified as an operating room hazard. OBJECTIVE To test among representative surgical personnel two different methods of improving safety performance: a demonstration/lecture session, and improved equipment arrangement on the operating field. METHODS A field experiment occurred in the classroom and in the operating room...

The present study aims to measure the number of cycles leading fracture (NCF) instruments in static and dynamic cyclic fatigue situations under body temperature stainless steel double-curved canals. framework was constructed establish movement occurring at a stable temperature. A step motor, holding system for an endodontic handpiece, created out artificial canal file mounted on handpiece. tota...

high speed wind tunnels are widely used in the study of fluid flow behavior around various objects. the air flow in the starting step of supersonic wind tunnels is transient including strong shock waves caused by the interaction of the tunnel main stream and the boundary layer at walls. to arrive in running step, the tunnel must be designed so as these waves leave immediately the test section. ...