• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.74-74
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• 2015

최근 홍수의 특성과 피해 양상은 과거와는 다르게 변화하고 있으며, 급격한 도시화로 인하여 기존 하천유역의 저류 능력이 감소하였으며 이러한 한계를 극복하기 위하여 이미 외국에서는 대심도 터널을 활용한 홍수재해 관리방안이 오래전부터 활용되어 왔다. 본 연구에서는 대심도 터널의 유입구, 수직갱, 감세지, 배수터널과 같은 시설물 중 대심도 터널 설계 시 수직 유입구를 통해 유입되는 유량의 에너지를 완화하고 효과적으로 배수 할 수 있도록 중요한 역할을 하는 감세지의 효율적인 깊이 산정을 위하여 수리모형실험을 실시하였으며, 모형은 Froude 상사법칙을 사용하여 원형의 1/18크기로 제작하였다. 본 연구에서 실시한 감세지 모형의 깊이는 0.278 m(원형 5.0 m), 0.417 m(원형 7.5 m)이며, 각 감세지 깊이별 수직 유입구 3개소(저지수직구1, 저지수직구2, 고지수직구) 및 5가지의 유량 CASE에 대하여 감세지 바닥면 압력을 비교?분석 하였다. 수직 유입구 3개소의 설계조건에 따른 감세지 깊이별 바닥면 압력 분포 평가를 실시한 결과 저지수직구1의 감세지 깊이 0.278 m(원형 5.0m)에서는 최대 압력이 4번 지점에서 $0.075kg/cm^2$(원형 1.30 MPa)이 측정 되었으며, 0.417 m(원형 7.5m)에서는 최대 압력이 1번지점에서 $0.089kg/cm^2$(원형 1.54MPa)이 측정되었다. 또한 저지수직구2의 감세지 깊이 0.278 m(원형 5.0 m)에서는 최대 압력이 1번 지점에서 $0.074kg/cm^2$(원형 1.28 MPa)이 측정 되었으며, 0.417 m(원형 7.5 m)에서는 최대 압력이 2번지점에서 $0.088kg/cm^2$(원형 1.52 MPa)이 측정되었다. 고지수직구의 감세지 깊이 0.278 m(원형 5.0 m)에서는 최대 압력이 3번 지점에서 $0.082kg/cm^2$(원형 1.42 MPa)이 측정 되었으며, 0.417 m(원형 7.5 m)에서는 최대 압력이 1번지점에서 $0.092kg/cm^2$(원형 1.59 MPa)이 측정되었다. 본 연구에서 실시한 수리모형실험의 결과 저유량에서 고유량으로 갈수록 최대압력지점은 반시계방향으로 움직이는 것을 알 수 있으며, 이는 수직 유입구의 설계조건에 따른 수직갱에서의 회전수차에 의하여 발생하는 것으로 분석하였다. 따라서 적절한 감세지 깊이 산정을 위해서 대심도터널의 수직 유입구(유입구형태, 수직갱)의 평가가 함께 유기적으로 이루어져야 할 것으로 판단된다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.8037-8045
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• 2015

The purpose of this study was to identify the effects of the application of elastic compression stockings and lower extremities exercise on edema and pain of lower extremities in hospital nurses. The participants were 30 hospital nurses working at a general hospital. The participants were categorized into three groups such as, 10 for an experimental group of the application of the elastic compression stocking, 10 for another experimental group of the application of Lower extremities exercise and 10 for a control group. Edema of the lower extremities were measured in terms of the girths of ankles and calves. And pain of the lower extremities were measured in terms of the score by NRS(Numerical Rating Scale). The data were analyzed with Frequency, Percentage, Mean, Standard Deviation, ${\chi}^2$-test and ANOVA to identify the participants' characteristics, SPSS Win 21.0 program was used for analysing. There are significant differences in lower extremity edema among the experimental group of lower extremities exercise, experimental group of elastic compression stocking and control group was supported(Rt Calf F=0.645, p=.000, Lt Calf F=21.941, p=.000). There are significant differences in lower extremity pain the experimental group of lower extremities exercise, experimental group of elastic compression stocking and control group was supported(Rt: F==7.320, p=.000 Lt: F=10.623, p=.000). In conclusion, in has been appeared that the lower extremities exercise and wearing elastic compression stocking have effedted in relieving low extremity edema and pain scale for nurses.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.729-734
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• 2017

A safety relief valve is a device that relieves excessive pressure in piping lines or tanks and maintains pressure at the appropriate pressure level for use. The (pressure in the) safety valve is directly influenced by the change in the back pressure, depending on whether the vents in the spring bonnet are vented to the atmosphere or to the outlet. The back pressure is divided into the built-up back pressure and the superimposed back pressure, and the back pressure characteristics vary according to the usage conditions. The safety valve used in this study is a Conventional Safety Relief Valve. The blowdown of the safety valve is predicted by establishing the equilibrium equation between the opening force and spring force considering the back pressure characteristics. Its reliability is secured by using CFX17.1. In addition, the safety of the safety valve trim was examined through fluid-structure interaction analysis.

• Tunnel and Underground Space
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• v.29 no.3
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• pp.157-171
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• 2019

The fracturing by liquid carbon dioxide ($LCO_2$) as a fracking fluid has been an alternative to mitigate the environmental issues often caused by the conventional hydraulic fracking since it facilitates the fluid permeation owing to its low viscosity. This study presents how $LCO_2$ injection influences the breakdown pressure, acoustic emission, and fracture morphology. Three fracturing fluids such as $LCO_2$, water, and oil are injected with different pressurization rate to the synthetic and porous mortar specimens. Also, the shale which has been a major target formation in conventional fracking practices is also tested to examine the failure characteristics. The results show that $LCO_2$ injection induces more tortuous and undulated fractures, and particularly the larger fractures are developed in cases of shale specimen. On the other hand, the relationship between the fracturing fluids and the breakdown pressure shows opposite tendency in the tests of mortar and shale specimens.

• The Korean Journal of Air & Space Law and Policy
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• v.5
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• pp.207-264
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• 1993

항공사의 외국인 소유는 이것으로 인하여 전체 항공운송 시스템이 변화될 수 있는 핵심적인 개념이다. 작금 항공운송산업을 둘러싼 환경은 급격하게 변화하고 있어서 많은 국가들이 항공사의 외국인 소유와 관련한 기존의 법제나 정책변경을 심각하게 고려하기 시작하였다. 항공기 및 항공사의 국적과 관련한 전통적인 개념은 양자사이에 '진정한' 또는 '효파적인' 관계가 있어야 한다는 것이다. 특별히 항공사의 '실질적인 및 효과적인 통제'조항은 양자 및 다자간 항공운송 협정에서 가장 핵심적인 역할을 해오고 있다. 그러나 변화의 바람이 거세게 일고 있다. 항공운송산업에서 이러한 변화는 미국에서 시작되고 미국의 국제항공관계에 적용되고 있는 규제완화에서 비롯되었다. 미국의 규제완화정책은 합병 및 흡수를 통한 항공사의 집중이라는 결과를 가져와서 항공운송 시장은 궁극적으로 소수의 거대 항공사에 의해 지배될 것이라는 우려를 낳고 있다. 이러한 새로운 추세에 대응하여 많은 국가틀이 다양한 형태의 지역협력체를 형성하고 있다. (예, EC, 아세안, 안데안 그룹, 야마스크로 선언 등) 또한 다수 국가들은 정치.경제적인 이웃에서 정부의 소유주식을 외국인 및 외국회사를 포함한 민간부문에 매각함으로써 사유.사영화를 추진하고 있다. 한편 제조업 분야에서 다국적기업 (IBM, 코카콜라 등)은 별 어력움이 없이 성립될 수 있다. GATT의 주관하에 열리고 있는 우루과이 협상에 참여하고 있는 국가들은 최혜국 대우, 내국인 대우, 시장접근 같은 상품교역의 개념및 원리를 항공운송서비스를 포함한 서비스교역에 적용하는데 기본적으로 합의하였다. 급격히 변화하는 환경에서 항공운송 산업만이 국가의 영공 주권, 항공사의 공익기업 개념, 상업적 이익의 균형교환 같은 자기류의 논리에 집착하여 언제까지나 홀로 고립될 수는 없을 것이다. 더구나 세계 항공운송 산업은 1980년 후반부터 큰 시련에 직면해 있다. 몇몇을 제외한 대부분의 항공사는 세계경제의 불황속에서 초과공급 및 운임전쟁으로 인한 엄청난 적자를 기록하고 있다. 모든점을 미루어볼 때 세계의 항공사들은 과거 어느 때보다도 외국인 투자를 필요로 하고 있으며 항공사가 속해 있는 정부는 외국인 소유에 관한 법제를 개정하고 나아가 전체 항공운송시스템을 개편하도록 압력을 받고 있다. 많은 국가에서 외국인 소유에 관한 법규의 개정은 현존 항공운송 시스템에 다각적인 영향을 가져올 것이다. 다시말하면 양자협상, 반독점및 경쟁볍규의 적용, 고용 및 카보타지등을 포함한 제반분야가 영향을 받을 것이다. 결국 외국인 소유에 관한 법제의 완화는 항공사의 세계화 또는 다국적화의 과정을 촉진시킬 것이고, 항공사간 다양한 형태의 제휴가 이러한 방향에서 계속될 것이다.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.14 no.1
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• pp.32-37
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• 2018

When designing high temperature piping system, creep phenomena must be considered. Since ASME code does not provide detailed methods of design by rule (DBR) for high temperature piping, Finite element analysis should be performed. However, In the case of piping system with frequent design changes, creep analysis of the entire piping system for every change is ineffective and practically impossible. Therefore, based on elastic and elastic-plastic analysis, which takes a relatively short time, the creep stress is predicted by using elastic follow-up factor method provided in R5 code and plastic-creep analogy presented by Hoff. The predicted creep stress for a virtual piping system was compared with the creep analysis result and the two results showed similar stress relaxation tendency in time.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.4
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• pp.36-44
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• 2009

Spray cross-section was measured by the Optical Line Patternator (OLP) and Optical Tomography at high ambient pressure. The laser line beam passed through the spray region, then Mie scattered signal and transmitted light were captured. The measured signal was processed to obtain a distribution of attenuation coefficient in spray cross-section. Beer-Lambert's law and mathematical reconstruction methods were used to reconstruct the distribution of attenuation coefficient. Spray became dense at high pressure and attenuation of scattered signal occurred seriously. OLP method, which uses Mie scattered signal, showed limit in compensating attenuation problem in dense spray region. Optical tomography reconstructed spray cross-section well, from transmission rate of light penetrating spray region.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.3
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• pp.96-103
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• 2019

In this study, a comparison was conducted to verify the propellant isolation assembly of the Korea Pathfinder Lunar Orbiter (KPLO). An engineering validation model (EVM) is being developed to simulate the flow of the flight model. Three factors were selected for comparison: the total pressure drop during propellant isolation assembly, the waterhammer by driving thruster valve, and the orifice set up for flow control and damping the waterhammer. The analysis results are compared with EVM test results. In the future, backup data to confirm the design will be established.

• Korean Journal of Optics and Photonics
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• v.5 no.3
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• pp.386-393
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• 1994

We have investigated output characteristics of XeCI excimer laser excited by transeverse electronbeam. We used e-beam output of 880 kV, 21 kA (70 ns, FWHM) and controlled current density of e-beam by pulsed magnetic coil (4.7 kG) which was fabricated around an e-beam diode (A-K gap is 21 mm) and laser chamber. We have obtained 35 J (4 atm) of e-beam deposition energy injected into laser media. The deposition energy was converted from an exposure area of Radcolor film and rising pressure of gas media which is measured by pressure jump method. The excited volume of $320cm^{3}$ was calculated. The maximum efficiency of 1.7% was obtained with the mixing ratio of HCllXe/Ar==0.2/ 6.3/93.5% and total pressure of 3 atm. Also laser output energy and specific energy were obtained 0.52 J and 1.7 J/I, respectively. For the analysis of experimental results we have developed computer simulation code. From the good agreements with the results of experiment and simulation we could theoretically explain the XeCI* formation channel. relaxation channel, and absorption channel of 308 nm.308 nm.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.6
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• pp.477-483
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• 2015

Investigations into cavity flows have been conducted for noise and vibration problems that arise in cavity systems. Cavity systems have been applied in engineering devices and have undergone rapid development in the aerospace industry. Meanwhile, to the author's best knowledge, the cavity on a curved wall has been seldom studied. The present work is conducted to study the flow physics of a cavity mounted on a curved wall. Numerical analysis is performed to investigate the cavity flow. Two variables of sub- and supersonic cavity flows were considered: the radius of curvature of the curved wall (L/R) and the inlet Mach number. The results show that the uniform vortex generated by the cavity flow on the curved wall stabilize the pressure fluctuation as time passes. As the inlet Mach number increases, the pressure fluctuation amplitude increases. The results obtained from the curved wall are compared with those from a straight wall using Rossiter's formula. The Strouhal number of the curved wall is lower than that of the straight wall. Lower Strouhal numbers have been obtained in the present computational fluid dynamics (CFD) results than in the theoretical results using Rossiter's formula.