The purpose of present study was to evaluate the influence of different base materials on the marginal integrity of posterior direct composite resin restorations. Conventional mesio-occluso-distal(MOD) cavity preparations, with margins in enamel and dentin, were prepared in 24 extracted human mandibular molars and randomly divided into four equal groups. One of three base materials (RMGI, compomer, flowable resin) was placed on the pulpal floors of the teeth of the groups. One group of teeth, which served as the control group, was not given any base material. Then, all teeth were restored with composite resin. The micromorphology of the tooth/restoration interfaces along the entire surfaces of the restorations was quantitatively analyzed using microscope at 150 magnifications immediately after finishing and after completion of thermo-mechanical stress. Marginal adaptation was assessed along the entire margin and % perfect margin (%PM) was calculated. The %PMs before and after thermo-mechanical stress in the groups were compared with Two- way ANOVA with Tukey test at the 95% confidence level. Before thermo-mechanical stress, there was no difference in marginal adaptation between groups. After the thermo-mechanical stress, the RMGI group showed the highest marginal adaptation rate among the tested groups. In compomer and flowable resin groups, the marginal adaptation was lower after thermomechanical stresses than before the stress (p<0.05).
With the recent progress in flexible manufacturing systems (FMS) in industry, increasing attention has been given to Automatic Guided Vehicle (AGV) systems. An AGV is a self-powered unit for transporting materials between stations without needing to be controlled by an operator. Such a system has several sensors to recognize the external state, and it is designed to travel between stations without external assistance. To manage each device quickly and independently it requires a distributed controller with a main computer as the host, as well as a number of micro-controllers. In this study, an AGV system with dual motor drive was constructed. A Pentium 4 personal computer was set up as the main host for the distributed control, and this communicated with other micro-controllers in the management of the motor. The speed of each motor was also controlled by a micro-controller.
Abstract:In general, the gears of mixer reducer for concrete mixer truck make use of the differential type planetary gear system to rotate mixer drum smoothly on the initial conditions. The planetary gear system is very important part of mixer reducer for concrete mixer truck because of strength problem. In the present study, calculating the gear specifications and analyzing the gear bending & compressive stresses of the differential planetary gear system for mixer reducer are necessary to analyze gear bending and compressive stresses confidently, for optimal design of the planetary gear system in respect to cost and reliability. As a result, analyzing actual gear bending and compressive stresses of the planetary gear system using Lewes & Hertz equation and verifying the calculated specifications of the planetary gear system, evaluate the results with the data of allowable bending and compressive stress from the Stress-No. of cycles curves of gears.
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