• Journal of Korea Society of Industrial Information Systems
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• v.13 no.4
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• pp.132-138
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• 2008

Small and medium-sized manufacturing companies have introduced production information systems such as pop and MES to improve their productivity. However, there has been little research on this field This study provides answers for 3 following critical questions for successful implementation of production information systems based on the literature review and case studies. First, do investments on this system bring the positive performance? Second, what are the critical success factors that should be managed? Third, how long does it take to obtain its performance? This paper suggests some implications for the practitioners.

• Proceedings of the KSRS Conference
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• 2008.03a
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• pp.53-58
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• 2008

인공위성을 통해 취득된 데이터들은 지상국의 수신처리시스템을 거쳐 표준영상으로 생산되며, 생산된 영상으로부터 사용자에게 의미 있고, 가치 있는 정보를 이끌어 내는 판독의 단계를 수행하게 된다. 본 연구에서는 원격탐사의 전반적인 이해를 돕기 위한 교육적 모델로서 캔샛 프로그램을 도입하였다. 캔샛 프로그램은 스탠포드대 로버트 트윙 교수의 제안으로 학생들에게 한 학기의 짧은 시간에 실제 인공위성의 설계, 해석, 제작, 조립, 시험, 발사, 운용 등 전반적인 시스템의 이해를 도모하기 위한 1Kg 이하의 캔 크기의 초소형 위성을 개발하는 교육 프로그램이다. 본 연구는 한국과학영재학교 R&E 프로그램의 지원으로 시작하였으며, 실제 초소형 위성 캔샛('KSAsat'으로 명명)을 직접 설계, 제작, 조립하고 최종적으로 발사 운용 시험을 수행하였다. 주 탑재체로 일반 상용 디지털 카메라를 장착하였으며, GPS, 광센서, 3 축 가속도계, 온도센서, 압력센서를 탑재하였다. 비행시험을 통해 성공적으로 영상을 취득하고, 각종 센서로부터의 데이터를 지상국으로 전송 받았다. 지상국을 통해 처리 되어진 데이터로부터 의미 있는 정보를 추출하는 판단의 단계를 거쳐 원격탐사의 전반적인 교육을 성공적으로 수행할 수 있었다. 본 논문에서 캔샛 프로그램이 원격탐사 교육에도 충분히 활용될 수 있음을 보였다.

• Aerospace Engineering and Technology
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• v.5 no.2
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• pp.174-180
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• 2006

The present paper describes transient thermal and mechanical analyses of a lox/kerosene type turbopump in a LRE(Liquid Rocket Engine). Turbopumps are used to pressurize propellants to achieve higher specific impulse of LRE. The turbopump under development has been designed and verified by structural analyses using finite element methods. Some parts of the turbopump operate under cryogenic environments, while the others work under ambient and high temperature environments. Therefore, numerical analysis at a turbopump system level is essential. In this study, casing assemblies of lox pump and fuel pump were analyzed to determine strength test and air-tightness test conditions. Also, some operational stress and strains of fuel pump casings were measured and analyzed. Based on these results, stress concentration of fuel pump casings during the operation could be successfully predicted.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.5
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• pp.439-444
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• 2003

Acoustic emission(AE) ran be very effectively applied to locate the damaged area in large structures by detecting the elastic waves generated during the damage process within solids. Source location in the composite structures has been, however, extremely difficult due to the acoustic anisotropy with the velocity dependence on fiber orientations. In this study, it has been shown that a newly proposed method for 2-D source location of anisotropic structures is practically applicable to the real structure. The method employes wave velocities obtained with different velocities from $0^{\circ}\;to\;90^{\circ}$ for a filament wound composite pressure vessel under the air-filled and the water-filled conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.6
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• pp.64-70
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• 2005

The overall results of hot firing tests of fuel-rich gas generator with impinging injector at design and off-design points are described. The gas generator consists of an injector head with impinging injector, a water cooled combustor wall, a turbulence ring to enhance mixing, an instrument ring measuring temperature and pressure and a nozzle. The combustion tests were successfully performed without damage of gas generator. Test results show that the outlet temperature is not dependent on residence time of hot gas within 4～6msec but dependent on chamber pressure. The relation between outlet temperature and combustion efficiency resulting from measured pressure, mass flow rate and area of nozzle throat is shown. The overall O/F ratio is the critical parameter to determine the outlet temperature and the linear correlation between two parameters is established.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.9-14
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• 2018

The function of gas springs is based on the compression of a gas. They are used in a wide variety of industries, and demand for them is increasing. Gas springs can be divided into compression and extension springs. Extension springs have not been studied much in relation to control of the piston speed, unlike compression springs. In this study, the magnitude of the piston rebound pressure was theoretically predicted by calculating the pressure loss in a double-cylinder extension gas spring. Numerical simulations of the piston behavior were carried out for small and large amounts of friction between the piston and the cylinder. FLUENT was used for the simulation with a 6-DOF model and UDF to simulate the behavior of the piston. The calculation regions of the front and rear of the piston were separated, and different types of grids were generated in the regions to implement a dynamic mesh using only a layering method. The results show that the piston returns with the target speed in both cases. However, the patterns of the piston behavior reaching the final speed are different.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.50-55
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• 2018

The important thing in extrusion technology is the design and production of molds. Appropriate design of the molds is essential for achieving the desired extrusion of molds at the same time to maximize the life of the molds and increase their efficiency. The extrusion temperature and extrusion speed are the main parameters at the time of extrusion. Different extrusion conditions should be added depending on the extrusion ratio, physical properties of the material, and type of extrusion. In this study, the extrusion process of various 6xxx series aluminum cast alloys for high speed train interior or exterior parts were investigated. The extruded die design was performed for the 6063, 6061, 6N01, 6005, 5083 and 6060 alloy profiles and an extrusion test was conducted. In addition, the extrusion conditions, such as extrusion pressure following as the billet temperature, extrusion temperature, and materials change, were analyzed. Although the 6063 aluminum alloy can be extruded at the lowest temperature and pressure, the 6061 alloy can be extruded at the highest temperature and pressure. From these results, the successful extruded products were manufactured from these established conditions.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.5
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• pp.62-70
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• 2015

A liquid rocket engine system can cause rapid pressure and temperature variations during the startup period. Thus the startup analysis is required to reduce time and expense for successful development of liquid rocket engine through the startup prediction. In this study, a startup analysis simulator is developed for a staged combustion cycle engine powerpack. This simulator calculates propellant flow rates using pressure and flow rate balances. In addition, a rotational speed of turbopump is obtained as a function of time by mathematical modeling. A startup analysis result shows that the time to reach a steady-state and a rotational speed at the steady-state are 1.3 sec and 27,500 rpm, respectively. Moreover it can indicate proper startup sequences for stable operation.

• Journal of Korea Water Resources Association
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• v.50 no.9
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• pp.609-616
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• 2017

In this study, algorithm for the selecting the optimum monitoring location and leakage detection algorithm based on back tracing calculation method were developed and verified by the experiments in pilot plant of water distribution system. First of all, optimum monitoring locations were selected and pressure changes were measured due to artificial leakage by pressure gauges in pilot plant. Simulations of leakage detection was performed for the verification of back tracing calculation method as a leakage detection method. From the results, it was found that leakage locations and leakage amount were exactly estimated. Various leakage amount from $0.0005m^3/s$ to $0.0018m^3/s$ were reproduced and leakage location was detected by back tracing calculation method. It was verified that back tracing calculation method as a leakage detection method is effective.

• Polymer(Korea)
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• v.38 no.1
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• pp.80-84
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• 2014

Polymer nanoparticles with cross-linked core and PBA/PS double-shell were synthesized and their baroplastic properties were characterized. PBA/PS, the inner and outer shell with cross-linked core consisting of St and DVB were synthesized by three-stage emulsion polymerization. The obtained materials exhibited pressure-induced mixing of their components and could be processed at $25^{\circ}C$ by compression molding which means there was no effect of the presence of cross-linked core. Interestingly, the Young's modulus of molded objects has found to be affected strongly by the size of double-shell nanoparticles. Furthermore, the molded object of higher PBA content was successfully recycled 5 times at $25^{\circ}C$ and showed 0.55 MPa of modulus and 1.81 MPa of strength at break.