• Microbiology and Biotechnology Letters
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• v.9 no.1
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• pp.35-44
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• 1981

Whole cell penicillin amidase of Escherichia coli was immobilized by entrapment in gelatin followed by extrusion and crosslinking with glutaraldehyde. The immobilized engyme preparation demonstrated the recovery yield of activity up to 70% and good stability during storage and operation. The half life of activity decay during the operation was estimated to be about 50 days. The optimum pH and temperature for both of immobilized and soluble enzyme are 8.5 and 5$0^{\circ}C$, respectively. No significant change was demonstrated in the effect of pH and temperature, but the increase in heat stability at high temperature was observed in the case of the immobilized enzyme. It was found that the plug flow reactor could be operated favorably since the pH drop along the column path due to tile reaction product was minimized by employing substrate solution with moderate buffer strength. The optimal condition of reactor operation was discussed with regard to the effect of substrate concentration and the residence time on the conversion efficiency and productivity.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.710-713
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• 2005

Recently, in the area of shipbuilding, automobile and electronics, the products which electroplating was applied to are developed and put into practice in the field. The extension of the field of applications electroplated objects is to complex shape and thus the rate of faults in electroplating is being increased in the process of manufacture. On the subject of the plating process in this study, the geometric factor, which influenced electroplating, was extracted by doing a comparative analysis of the findings in the plating bath and the results of performing computer simulation of 3D. Considering these factors, the study on the optimization of designing was conducted to make the plating quantity of plated objects uniform in terms of 3D.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.107-114
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• 2017

A turbocharger is an engine supercharger that is driven by exhaust gas. It improves the output and fuel efficiency by increasing the charging efficiency of the mixture gas, which is achieved by changing the rotatory power of the turbine connected to the exhaust passage. It is important to control the supercharging for this purpose. A nozzle slide joint is one of the core parts. Austenitic stainless steel is currently used as the material for this part, and its excellent mechanical properties include high heat resistance and corrosion resistance. However, because of its poor machinability, there are many difficulties in producing products with complicated shapes. Machining is used in the production of nozzle slide joints for high dimensional accuracy after metal powder injection molding. As design variables in this study, we investigated the sintering temperature, product stress, deformation rate, radius of curvature of the punch, and angle of the chamfer punch, which are related to the strain and shapes. The goal is to suggest a forming process using Nitronic 60 that does not require machining to manufacture a nozzle slide joint for a turbocharger. Accordingly, we determined the best process environment using finite-element analysis, the signal-noise ratio, and the Taguchi method for experiment design. The relative density and hydrostatic pressure of the final product were in accordance with the results of the finite element analysis. Therefore, we conclude that the Taguchi method can be applied to the design process of metal powder injection molding.

• Design & Manufacturing
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• v.13 no.2
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• pp.17-21
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• 2019

In this study, selective laser sintered 3D printing mold core and metal core were used to investigate the difference of the thickness shrinkage from the gate of the injection molded part at a constant interval. SLS 3D printing mold core was made of nylon-based PA2200 powder and the metal core was manufactured by conventional machining method. As the PA2200 powder material has low strength, thermal conductivity and high specific heat characteristics compared with metal, molding conditions were set with the consideration of molten temperature and injection pressure. Crystalline resin(PP) and amorphous resin(PS) with low melting temperature and viscosity were selected for the injection molding experiment. Cooling time for processing condition was selected by checking the temperature change of the cores with a cavity temperature sensor. The cooling time of the 3D printing core was required a longer time than that of the metal core. The thickness shrinkage of the molded part compared to the core depth was measured from the gate by a constant interval. It was shown that the thickness shrinkage of the 3D printing core was 2.02 ~ 4.34% larger than that of metal core. In additions, in the case of metal core, thickness shrinkage was increased with distance from the gate, on the contrary, in the case of polymer core showed reversed aspect.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.3
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• pp.553-558
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• 2019

Global auto parts companies are making efforts to develop EWP(: Electric Water Pump) which is one of the core parts of environment friendly car. In eco-friendly automobiles, an independent cooling system is used rather than a cooling system that is linked to an internal combustion engine. Therefore, the research and development of the water pump operating separately from the engine and the related production system are being actively carried out. In order to overcome the shortcoming of EWP of PPS material suitable for injection system, G company which is a global parts company that researches and develops EWP around SUS and is in the process of developing robot-based production equipment for mass production. In this paper, a heat shock simulation system is designed and implemented that works with the robot-based production system to test the performance of the produced EWP. By using this system, it is possible to test the EWP in an virtual environment similar to the actual environment, thereby reducing the defect rate of the product. At the same time, all the data produced during the entire process for testing can be stored, which can be utilized in the future development of CPS(: Cyber Physical System) of EWP system based on big data.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.2
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• pp.127-135
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• 2022

Compared to the continuous increase of domestic nano-satellite development cases, the initial communication success rate is relatively low. In a situation where communication cases of LEO satellites using commercial satellite communication networks are increasing recently. In this situation, the SNIPE project developed by the KASI(Korea Astronomy and Space Science Institute), KARI(Korea Aerospace Research Institute), and Yonsei University apply an Iridium module for communication test to the SNIPE nano-satellites. Therefore, in this paper, the visibility analysis of the iridium module on the SNIPE satellite was analyzed under considering the orbital and communication environment of the iridium satellite constellation and the attitude control mode. In the case of LEO satellites, the communication possibility was limited due to the relatively small iridium communication coverage for high altitude and the high doppler shift considered in the iridium communication network. For this reason, in this paper, it could be simulated that there was a more performance difference according to the difference in relative RAAN(Right Ascension of Ascending Node) angle with the Iridium constellation. Finally, by checking the visibility of communication module under the tumbling situation that occurred during the initial deployment of the nano-satellite, the possibility of using the iridium communication technology was analyzed.

• Restorative Dentistry and Endodontics
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• v.34 no.2
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• pp.130-136
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• 2009

The aim of this study was to develop a method for measuring the slumping resistance of flowable resin composites and to evaluate the efficacy using rheological methodology. Five commercial flowable composites (Aelitefil flow:AF, Filtek flow:FF, DenFil flow:DF, Tetric flow:TF and Revolution:RV) were used. Same volume of composites in a syringe was extruded on a glass slide using a custom-made loading device. The resin composites were allowed to slump for 10 seconds at $25^{\circ}C$ and light cured. The aspect ratio (height/diameter) of cone or dome shaped specimen was measured for estimating the slumping tendency of composites. The complex viscosity of each composite was measured by a dynamic oscillatory shear test as a function of angular frequency using a rheometer. To compare the slumping tendency of composites, one way-ANOVA and Turkey's post hoc test was performed for the aspect ratio at 95% confidence level. Regression analysis was performed to investigate the relationship between the complex viscosity and the aspect ratio. The results were as follows. 1. Slumping tendency based on the aspect ratio varied among the five materials (AF