This study is about the optical properties of InP-based quantum dot nanoparticles depending on their core/shell structure. The need to synthesize non-cadmium-based quantum dot nanoparticles with high quantum efficiency has become necessary due to the harmful effects of the element cadmium. We synthesized three types of quantum dot nanoparticles in 2000ml three-necked flasks by varying the synthesis temperature and time to have the same PL spectra according to the composition of the core and shell. The PL spectra, absolute quantum efficiency, and nanoparticle size were compared and analyzed according to the composition at red emission wavelengths of 614, 616, and 630 nm. InP/ZnSe/ZnS nanoparticles were synthesized with the highest PL-AQY of 94% at 614 μm, and Ga-doped InP/GaP/ZnSe/ZnS nanoparticles were synthesized with the highest PL-AQY of 97% at 616 μm. InZnP/ZnSe/ZnS nanoparticles with alloy cores were able to synthesize quantum dot nanoparticles with a peak PL-AQY of 98% at 630μm.

This study aimed to a sign device using quantum dot film. We synthesized quantum dots with an absolute quantum yield of more than 95% using the solution process method, coated the quantum dot film by mixing it with acrylate resin, made a sign device, and studied the improvement of visibility, and obtained the following conclusions. Quantum dots with absolute quantum yield of 97.63% at 535 nm and 97.85% at 615 nm were synthesized by doping InP with GaP and stacking ZnSe and ZnS composite shells. The synthesized quantum dots were mixed with acrylate syrup at a weight ratio of 10% to coat a film with a luminance uniformity of more than 95%, and the quantum dot film was attached to a luminous display with an insulation capacity of 500 V, an insulation resistance of 99.9 GΩ, and a luminance of 688.5 ㏅/㎠ at white region and 122.3 ㏅/㎠ at red region.

This study aimed to grow single crystals with low dislocation density using a heat exchange method using room temperature water, and investigated the effect of the structure of the heat exchanger under the crucible on the defects and dislocation density of the single crystals and the shape of the solid-liquid interface of the crystals, and obtained the following conclusions. The dislocation density of sapphire single crystal grown at 2,200℃ for 30 min and a growth rate of 0.2℃/min was 0.92x103pcs/㎠. Mo guard was used to stabilize the solid-liquid interface grown from seeds, and sapphire single crystals with a diameter of 130㎜ and a height of 75㎜ were grown.

This study investigated how to repair high-pressure pipes by applying the expansion method instead of the welding method used to repair pipes in the steel, petrochemical, and shipbuilding industries that use high-pressure pipes, and developed a pipe-specific expansion device and auxiliary equipment to use the expansion pipe. We developed an expansion device with a range of 65A to 125A, evaluated the characteristics of the equipment, and manufactured high-pressure pipes made with this device, and obtained the following conclusions. The pressure resistance performance test of the non-welded expansion device was carried out at 32A to 125A, and the pipe pressure resistance test showed good results, and the durability test confirmed the durability of 0.0061 to 0.0063mm. The vibration test of the developed expansion device was measured at 0.3~0.5mm/s, and the noise measurement result was 65.1~65.5 at 32A, 65.2~65.5 at 65A, and 65.4~66.6dB at 125A.

This study described a way of developing a resin for deviceizing quantum dots. Furthermore, the following conclusions were obtained by developing light curable syrup and UV curable syrup. First, The viscosity of the mixed resin decreased as the content of the diluent increased, and the value was bewteen 4,310 and 1,473cps. Second, haze was measured by using NDH 5000, and all of the synthesized syrups were obtained a haze value of 1% or less with a transmittance of 95% or more in the visible light region. Third, the viscosity of the mixed resin decreased as the temperature increased, and at this point, the viscosity showed a value of 4,219 to 1,128cps. Lastly, As a result of measuring the viscosity of the resin before and after mixing the quantum dot nanoparticles, it appears to be little change.

In this study, a mixed resin containing Bis-GMA was developed to produce a light-emitting sign using quantum dots. As a result of measuring the viscosity, color coordinates change, and luminance of the mixed resin, the following conclusions were obtained. The viscosity of the mixed resin decreased as the content of the diluent increased, and viscosity values ​​ranged from 3,627 to 1,349cps showed as a result. The viscosity of the mixed resin decreased as the temperature increased, and the viscosity showed a value of 5,156 to 1,132cps. For the optical properties of InP/GaP/ZnSe/ZnS quantum dots, the absolute quantum efficiency was 91% at 522nm and 90% at 618nm when the gallium was 0.01%. The luminance of the light-emitting sign using the resin mixed with quantum dots was showed 142.6cd/m2 in white and 104.2cd/m2 in the red region.

This study was to develop a piston rod made of SiC by applying a sintering treatment after press molding in order to replace the imported piston rod used in the past. As a result of evaluating the mechanical properties of the developed piston rod, the following conclusions were obtained. The surface roughness value of the piston rod made of silicon carbide was 0.950Ra, and the surface Vickers hardness value was 19.94GPa. As a result of XRD analysis of the surface of the prototype piston rod, the main crystalline phase was 6H-SiC, and the crystalline phases of 4H-SiC and α-SiC were existed. In addition, a trace amount of SiC was detected. As a result of SEM observation of the piston rod surface of the prototype, a number of large porosity were observed. As a result of measuring the surface hardness of the piston rod made of SiC, it showed 70% of the physical properties compared to imported products.

In this study, in order to manufacture STS 316L seamless pipes with 18mm, 25mm, and 42mm diameters that can be used for high pressure, we intend to make predictions through design and finite element analysis and produce real objects. It was measured to have the highest hardness value in the deformed part, and it is expected to be due to work hardening. It has been interpreted that plastic deformation does not occur up to 1,000bar for STS 316L seamless pipes with a diameter of 18mm and 25mm, but plastic deformation occurs at 900bar or more in STS 316L seamless pipes with a diameter of 42mm.

This study has described as a way of establishing an automated system that allows sorting of living fish caught at sea by weight, and producing and testing as prototypes. The live fish that applied for this research is named as a croaker. 30(thirty) times of measurements with the fishes were applied for screening initially. As a results, it was the highest deviation rate of 19.7% within 2g of their initial weight. In addition, it showed the lowest deviation rate of 8.2% below 10g of them. Throughout the measuring experiments, it was found that the error that occurred during weighting was friction with the upper surface of the load cell on the circular sorting plate. Once the friction was removed, it was figured out that the average deviation in weight per each fish was measured as 0.76g. This error should be able to be eliminated by improving the material of machine elements, the surface material of the load cell. Under this circumstance, this pilot test in sorting living fishes by weight was brought adequate results. The existing sorting device was performed at 4,500 fishes per hour as a sorting speed. The sorting device developed in this research improved productivity by over 33% by setting the sorting speed in 6,000 fishes per hour.

The purpose of this study was to develop high quality dark film honeycomb fabric curtains. The results of producing the prototype for various color tone development, hot melt viscosity, and adhesiveness test for the final prototype were as follows. The hexagonal honeycomb structure is easy to manufacture, has a good coupling force, and has a dark honeycomb fabric curtain. The hot melt condition was obtained with 540g of hot melt and 1.5kg of diluent, 242.3cp, and the curing result was obtained at 140°C. Seven different colors were developed using yellow, red, blue, and white four primary colors. The adhesive force test device was designed to enable more than 5,000 real tests by the automatic opening and closing device for the convenience of the field workers. The size of the test sample was designed to be 1,000mm × 1,200mm. As a result of designing and manufacturing the prototype to attach the monitor and the control device to automatically count, the prototype was made to be measured 10,000 times. The combined force of the honeycomb fabric curtain was maintained after 5,000 tests on the manufactured rock film honeycomb fabric curtain.

In this study, attention has been focused on magnesium materials, which are widely used for lightening of electronic products and mobile phones. Therefore, a polishing apparatus was fabricated by replacing the SiC abrasive used for polished surface of magnesium plate with a ceramic abrasive. The following conclusions were obtained. It is believed that the increase in productivity of 50% compared to the conventional cross-sectional polishing due to the double-side polishing of magnesium sheet can contribute to increase the company's sales. The surface roughness was measured by polishing the plate using a magnesium plate mirror polisher. The Ra, Rmax and Rz values were 0.43, 0.54 and 0.54, respectively. In this study, the optimum polishing speed was 800 m/s when the surface was polished with a magnesium surface polishing device designed and manufactured as a prototype.