The material in powder state has long been used by selective laser sintering (SLS) for making rapid prototyping (RP) parts. A new approach to fabricate smoother surface roughness RP parts of ceramic material from slurry-sate has been developed in this study. The silica slurry was successfully laser-gelling in a self-developed laser sintering equipment. In order to overcome the insufficient bonding strength between layers, a strategy is proposed to generate ceramic parts from a single line, a single layer, to multi-layers of gelled cramic in this paper. It is found that when the overlap of each single line is 25% and the over-gel between layers is 30%, stronger and more accurate dimensional parts can be obtained under a laser power of 15W, a laser scanning speed of 250 mm/s, and a layer thickness of 0.1 mm. The 55:45 wt. % of the proportion between the silica powder and silica solution results in suitable viscosity of the ceramic slurries without precipitation. Furthermore, the effects of process parameters for the dimensional accuracy and surface roughness of the gelled parts are investigated and appropriate parameters are obtained.
This paper presents a Modified model reference adaptive system (MMRAS) speed controller for speed estimation of induction motor using model-reference adaptive scheme (MRAS) approach in a direct torque control system. A good speed controller of induction motor can enhance the speed estimation of sensorless drives. The MMRAS controller can reduce effect of parameter variations and nonlinearities in the induction motor, and approaches to desired performance of referenced model. So, the presented controller can enhance the performance of speed estimation. The availability of the proposed structure scheme is verified by through under computation simulations with MATLAB software. Simulation results are presented in order to prove the availability of the proposed structure scheme.
In this work, a hydroxyapatite (HA) bioceramic and a silica binder were used as the raw materials for manufacturing bioceramic bone scaffold after sintering by a laser beam in a home-made 3D Printing (3DP) machine. Results indicate that the bending strength of the scaffold can be improved after heat-treatment. While simultaneously increasing surface roughness conducive to osteoprogenitor cell adhesion. The processing parameters of a 90 mm/s laser scanning speed, 12 W of laser energy and 10 kHz of scanning frequency were used to fabricate a porous scaffold model, which possesses suitable biocompatibility and mechanical properties, allowing adhesion and proliferation of bone cells. Therefore, this process has great potential for manufacturing bone scaffolds.
A gravity-based power generation apparatus comprises a main body, which comprises a cylinder and coils. When the magnetic ball is affected by gravity, and vertically moves in the cylinder inside, coils generate electrical power by the electromagnetic effect. The power supports to a lighting unit and a USB unit. The apparatus is used as an emergency device, supported a gravity-based flashlight and a mobile USB power. The apparatus is implemented by 3-D printer. The experiment results show idea and apparatus are effective.
In this paper, the hydroxyapatite (HA) based bioceramic materials were used in a rapid prototyping (RP) system to fabrication bioceramic bone scaffold for tissue engineering (TE) using an additive manufacturing (AM) technology. When the bioceramic slurry is sintered via the processing parameters of an 85 mm/s laser scanning speed, 24.5 W of laser power, 10 kHz of scanning frequency, and 2500 Cp of slurry viscosity, a porous bone scaffold can be fabricated under a lower laser power energy. Results indicate that the bending strength of the scaffold was 14.2 MPa, which could be improved by heat-treatment at 1200 °C for 2 hour. MTT method and SEM observations confirmed that the fabricated bone scaffolds possess suitable biocompatibility and mechanical properties, allowing smooth adhesion and proliferation of osteoblast-like cells. Therefore, the fabricated bone scaffolds have great potential for development in tissue engineering.
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