영상기법을 이용한 수직상향 기포유동에 관한 연구

서동표,오율권 한국마린엔지니어링학회 2003 한국마린엔지니어링학회지 Vol.27 No.5

In the present study, the characteristics of upward bubble flow were experimentally investigated in a liquid bath. The velocity of upward bubble flow was calculated for two different experimental conditions:1) bubble flow without kinetic energy 2) bubble flow with kinetic energy. Bubble flow without kinetic energy starts to undergo the effect of buoyancy l0cm away from the nozzle. Whereas. kinetic energy is dominant before 30 cm away from the nozzle in bubble flow but after this point kinetic energy and inertial force are applied on bubble flow at the same time In addition, as the flow rate increases the maximum velocity point moves to the nozzle. The velocity Profiles near free surface is extremely irregular due to surface flow. Gas volume fraction is high near the nozzle due to gas concentration. but decreases with the increasement of axial position. Gas volume fraction does not vary after the axial position, z=60 in spite of the increasement of flow.

수직상향 기체 주입에 따른 기포 및 액상의 유동분석

서동표,오율권 대한설비공학회 2003 설비공학 논문집 Vol.15 No.9

In the present study, a PIV measurement and image processing technique were applied in order to investigate the flow characteristics in the gas injected liquid bath. The circulation of liquid was induced by upward bubble flow. Due to the centrifugal force, the flow was well developed near both wall sides than in the center of a bath. The vortex flow irregularly repeated generation and disappearance which helped to accelerate the mixing process. The bubble rise velocity in the bottom region was relatively lower than in the upper region because the energy generated by bubbles' behavior in the region near the nozzle was almost converted into kinetic energy But bubble rise velocity increases with the increase of the axial distance since kinetic energy of rising bubbles is added to buoyancy force. In conclusion, the flow increased bubble rise velocity and the flow of the bottom region became more active.

기체 주입 시스템에서 기-액 상호작용에 관한 연구

서동표,황세준,오율권 朝鮮大學校 機械技術硏究所 2001 機械技術硏究 Vol.4 No.1

Gas-injected system can be applied to various field such as metallurgical and chemical processing operations. So this study aims at presenting the relevant relationship between gas phase and liquid phase in gas-injected bath. The volume fraction, velocity, and temperature distribution of each phase were measured in order to predict the flow characteristics in gas-injected system. The gas discharged into the liquid bath loses its kinetic energy in a short distance from the nozzle exit, and then rises with a relatively uniform velocity due to buoyancy. As the gas rises upward in the liquid, the liquid entrains into the rising gas and a gas-liquid two-phase plume forms. In vertical injection systems, the gas-liquid plume is symmetric about the axis of the injection nozzle. In the region close to the orifice exit, the flow variables show steep spatial changes in both directions along the plume and across the plume. This region can be charaterized as a developing flow region.

수평원관내에서 3상 혼합물의 유동특성에 관한 실험적 연구

서동표,정경진,오율권 朝鮮大學校 機械技術硏究所 2000 機械技術硏究 Vol.3 No.1

Petroleum is one of the most important energy. Recently, it is common to transport petroleum by an pipeline network than by an oiler. However, in this case, serious problem is that we have small knowledge of flow dynamics dealing with multiphase mixture. So the purpose of this study is to show the flow characteristics of the three phase flow among water, oil and air in the horizontal pipe and supply necessary data to engineers who design transport pipes. In order to investigate of a flow characteristics, the experimental results were compared each other on the basis of observations between oil and water, oil and air, and water and air.

기포운동에 따른 2상유동 특성에 관한 연구

서동표,오율권 대한설비공학회 2003 설비공학 논문집 Vol.15 No.4

In the present study, the characteristics of upward bubble flow were experimentally investigated in a liquid bath. An electro-conductivity probe was used to measure local volume fraction and bubble frequency. Since the gas is concentrated at the near nozzle, the flow parameters are high near the nozzle. In general their axial and radial values tended to decrease with increasing distance. For visualization of flow characteristics, a Particle Image Velocimetry (P.I..V) and a thermo-vision camera were used in the present study. The experimental results show that heat transfer from bubble surface to water is largely completed within z=10mm from the nozzle, and then the temperature of bubble surface reaches that of water rapidly. Due to the centrifugal force, the flow was more developed near the wall than at bubble-water plume. Vortex flow in the bottom region was relatively weaker than that in the upper region.

Mid-Loop Operation 자유수면 와동현상에 관한 실험적 연구

서동표,오율권 朝鮮大學校 機械技術硏究所 2000 機械技術硏究 Vol.3 No.2

While the mid-loop of nuclear power station is in operation it is need to determine the relation of suction flow rates with in the pipe arrangement for preventing air suction phenomena caused by a free surface vortex. Therefore, in this study, correlationships between the dimensionless numbers such as submergence H/d, Froud number, Reynolds number was not as dominant as Froude number. Moreover, a modified inlet device, while is reduce type with vortex breaker has strongly been recommended for the prevention of air entrainment.

가스가 주입된 용기에서 기공율, 기포빈도와 온도측정에 관한 연구

박설현,오율권,서동표 朝鮮大學校 機械技術硏究所 1999 機械技術硏究 Vol.2 No.2

The local phase volume fraction, bubble frequency and the phase temperature distributions were measured in vertical air injected water baths. An electroresistivity probe was employed for the determination of the local void fraction and bubble arrival frequency. The phase resolved temperatures were measured using a microthermocouple. The thermocouple signals were digitally filtered, and were carried out to characterize the overall structure of the gas-liquid plume and the heat transfer mechanism between the phases.

수직상향 기체주입 모델에서 유동구조에 관한 연구

서동표(Dong-Pyo Seo),홍명석(Myung-Seok Hong),오율권(Yool-Kwon Oh) 대한설비공학회 2003 대한설비공학회 학술발표대회논문집 Vol.2003 No.-

중소기업의 ERP 시스템 도입효과 분석

서동표(Dongpyo Seo),홍용식(Yongsik Hong),최강화(Kanghwa Choi) 한국생산관리학회 2010 한국생산관리학회지 Vol.21 No.4

본 연구에서는 글로벌 무한 경쟁시대에 중소기업 경쟁력강화의 핵심수단으로 활용되고 있는 중소기업의 ERP 시스템 도입효과에 대해 분석하고자 한다. 즉, 본 연구에서는 중소기업의 ERP 시스템 도입효과에 대한 실증분석을 수행하기 이전에, 기존의 ERP 시스템의 도입 및 운영에 대한 선행연구들을 바탕으로 ERP 시스템의 도입과 운영에 관한 인과관계 분석을 수행하였다. 이를 통하여 국내 중소기업의 ERP 도입 및 운영에 따른 긍정적인 효과와 부정적인 효과를 이론적으로 살펴보고, 이와 같은 각 인과변수들 간의 순환적인 인과관계를 파악하여 인과지도를 작성하였다. 또한 이와 같은 인과지도를 기반으로 중소기업 정보화혁신전문기업(TIMPs) 지원을 받아 ERP 시스템을 구축한 중소기업과 제반 여건이 비슷한 ERP 시스템을 미도입한 기업 간의 재무성과의 차이를 살펴봄으로써, 인과구조 상의 자기강화 루프와 자기균형 루프들 간의 상충적인 관계를 살펴본다. 이를 통해 중소기업의 효율적 ERP 운영을 위한 정책적 방안을 제시하고자 한다. 중소기업 정보화 지원을 받아 ERP 시스템을 구축한 중소기업과 비교기업 간 재무성과 차이 분석의 결과를 살펴보면, 활동성의 경우에만 ERP 도입 후 2년차부터 통계적으로 유의한 차이를 보였으나 수익성, 안정성, 성장성, 생산성 세부지표들은 대부분이 ERP 시스템 도입기업과 미도입기업 간에 통계적으로 유의하지 차이를 보이지 않았다. 그러나 이러한 결과가 정부의 중소기업 정보화 지원 사업이 효과가 없다거나 불필요하다는 것을 의미하는 것은 아니며, ERP 시스템 도입 후, 사후단계의 정보 시스템 유지보수 및 효율적 사후운영 관리가 더욱 필요함을 역설적으로 보여주고 있다. 또한 본 연구에서 살펴본 정량적 지표 이외에 기본의 연구들에서 살펴 본 정성적 효과까지 고려한다면, 중소기업의 ERP 시스템에 대한 투자는 중소기업의 효율적인 운영을 위한 정책적 대안이 될 것으로 판단된다. The objectives of this research was to investigate the impact of ERP system on firm's financial performance. Upon the conflicting results of previous a few studies on ERP's impact on firm performance, this study tries to make the financial comparison between ERP-adopted and ERPnot-adopted firms among major Korean SMEs through a matched sample comparison group methodology and publicly available financial data. The Korean SMEs (supported by The Small & Medium Business Administration: TIMPs) have been heavily investing in ERP in recent years and expect that ERP can help them gain superior financial performance. Given the high costs and high risk of ERP investments, to quantify the financial benefits of ERP implementation is an important research issue. This paper empirically examines the impacts of ERP implementation on firm performance using the financial data from 30 Korean SMEs that implemented ERP. As a result, the ERP implementation does not reveal significant performance improvement during the implementation period and the three-year post-implementation period and even a decline in performance during the first two years after implementation. However, a slight performance improvement in the third year after implementation may indicate that the financial benefits of ERP may show after a long period of ERP use. These results can provide a valuable insight for Korean SMEs that want to invest in ERP. The contribution of this research shows how these critical success factors(CSF) were nterrelated and influenced each other directly or indirectly for performance improvement using a causal loop diagram model.

기-액 기둥에서 기포유동에 관한 연구

서동표(Dong-Pyo Seo),홍명석(Myung-Seok Hong),오율권(Yool-Kwon Oh) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4

The characteristics of upward bubble flow were experimentally investigated in a liquid bath, In the present study, a thermal-infrared camera and high speed CCD camera were used to measure their temperature and local rising velocity, respectively. Heat transfer from bubble surface to tater is largely completed within z=10mm from the zozzle, and then the temperature of bubble surface reaches that of water rapidly. The rising velocity of bubble was calculated for two different experimental conditions: 1) bubble flow without kinetic energy 2) with kinetic energy. Bubble flow without kinetic energy starts to undergo the effect of inertia force 10cm away from the nozzle. Whereas, kinetic energy is dominant before 30 cm away from the nozzle in bubble flow, but after this point, kinetic energy and inertial force are applied on bubble flow at the same time.