• 한국분무공학회지
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• 제23권4호
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• pp.159-168
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• 2018

Thrust throttling in a liquid rocket engine can be implemented via several ways such as high pressure drop injector, dual manifold, multiple chamber, pintle injector, and gas injection. Thrust throttling using gas injection controls thrust by usually injecting inert gas into propellant through an aerator to reduce the propellant's bulk density. In this study, the outside-in aerator was used in the propellant line to create two phase flow. Closed-type, open-type, and screw-type bi-swirl coaxial injectors were utilized for investigating throttling characteristics such as pressure drop, mixture density, and discharge coefficient according to gas-liquid mass ratio.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.313-317
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• 2009

액체추진제로켓엔진의 추진제 공급유로 내 압력보정을 목적으로 설치된 오리피스는 엔진의 시동 및 정지시, 압력파를 발생시키는 원인이 되며 압력파로 인한 저주파 불안정을 막기 위해서는 오리피스의 개도에 따른 동특성의 변화를 살펴볼 필요가 있다. 오리피스의 동특성 변화를 확인하기 위해 오리피스 공급 압력을 급격하게 증가하도록 하였고 오리피스의 개도를 바꿔가며 동적인 압력변화를 측정하였다. 오리피스의 개도가 증가함에 따라 오리피스에 의한 수격현상은 감소하였으며 오리피스 하류의 수력학적 영향이 지배적으로 나타나는 것을 확인하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.1038-1044
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• 2017

액체 로켓 엔진의 터보펌프를 구동하는 고압 초음속 충동형 터빈의 로터 블레이드에 3차원 설계 요소를 적용하여 성능을 개선하기 위한 연구를 진행하고 있다. 본 논문에서는 기존 설계된 터보펌프용 터빈의 로터 블레이드 형상을 바탕으로 로터 블레이드에 스윕(sweep)과 상반각(dihedral) 등과 같은 중첩선(stacking line) 변화를 통한 3차원 형상을 적용하고 CFD를 이용한 3차원 유동 해석을 수행한 후, 각각의 설계 요소에 대한 터빈성능 특성 변화를 면밀히 검토하고 그 결과를 정리하였다.

• Bulletin of the Korean Chemical Society
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• 제8권2호
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• pp.105-110
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• 1987

A theory in which the Enskog hard sphere collisional dynamics complements the hydrodynamic theory is applied to the fast modulation dephasing dynamics in liquids which leads to homogeneous line broadening in the isotropic Raman spectra. The dephasing times of several molecules in pure liquids and in trace solutions in the solvent $CCl_4$ are calculated and these are compared with experimental values. The temperature dependence of the dephasing time of liquid acetonitrile and the isothermal density dependence of the dephasing time of liquid methyl iodide are also investigated.

• Asian Journal of Atmospheric Environment
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• 제11권1호
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• pp.54-60
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• 2017

Quantifying the trace elements in infinitesimal ambient liquid samples (e.g., single raindrop, cloud/fog water, and the soluble fraction extracted from the particles collected for a short time) is an important task for understanding formation processes, heating/cooling rates, and their health hazards. The purpose of this study is to employ an in-air micro PIXE system for quantitative analysis of the trace elements in a thimbleful of reference liquid sample. The bag type liquid sample holder originally designed with $10{\mu}m$ thick $Mylar^{(R)}$ film retained the original shape without any film perforation and apparent peaks of film blank by the end of the analysis. As one of tasks to be solved, the homogeneity of the elemental distribution in liquid reference species was verified by the X-ray line profiles for several references. It was possible to resolve the significant peaks for whole target elements corresponding to the channel number of micro-PIXE spectrum. The calibration curves for the six target elements (Si, S, Cl, Fe, Ni, and Zn) in standard solutions were successfully plotted by concentration (ppm) and ROI of interest net counts/dose (nC).

• 대한화학회지
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• 제63권1호
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• pp.12-23
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• 2019

The new experimental data of liquid-liquid equilibrium (LLE) of aqueous two-phase system (ATPS) consisting of poly(ethylene glycol) 3000 + tri-potassium citrate at different pH were presented. It was found that an increase in pH resulted in the expansion of the two-phase region. The TLL and STL increased with increasing the pH values. The Merchuk equation can be appropriately employed to correlate the binodal curves and also the tie-line compositions were adjusted to both the Othmer-Tobias and Bancroft equations. In order to calculate the compositions of the phase and the ends of the tie-lines, density and refractive indices as two physical properties were used. Finally, the extended UNIQUAC, UNIFAC, Virial-(Mobalegholeslam & Bakhshi) and modified UNIQUAC-FV were used to measure the phase equilibria at different pH. The results of the models suggested that it can be used quite well to correlate the LLE in an aqueous solution of polymer-salt.

• 패션비즈니스
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• 제20권6호
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• pp.94-110
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• 2016

A necessity for infants, diapers are not only used over long durations, but are also in direct contact to the infants' skin, making the choice of diaper to be of utmost importance. Current interest in cloth diapers is rapidly increasing because of issues concerning the baby's health, green environment, and economy. However, previous researches on cloth diapers are limited to simply investigating the form and material of commercial cloth diapers. There are few in-depth researches for the optimal cloth diaper development. This is therefore a fundamental research for the development of optimized cloth diapers, and analyzes the difference in absorption depending on the placement of seam line (liner, darts, and I pattern), the locations of liquid spraying (1 cm and 8 cm ahead of the center), and the amount of liquid capacity (10 and 20 ml). Currently, the development of diaper patterns considers the crotch shape of the infants and the skin length deformation. As a result, in the case of the I-pattern, the horizontal seam line prevents water from spreading to the front and back, thus reducing the absorbed area. This result was more clearly visible when water was sprayed at the center. The effect of the seam line became more obvious when there was more water (20 ml); also, when water was sprayed at the center, more leakage was observed. Using the results of this research, implementation of horizontal seam is expected to prevent the upward spread of urine.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.49-51
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• 2006

A new data line reduction driving method was developed for high pixel density LCoS microdisplays. Its pixel structures and its corresponding gate line waveform were proposed, too. This idea can fulfill the increasing demand for higher resolution LCoS. In this method, no additional AC power is dissipated, and no more horizontal line time is needed. So this method can be applied to the high resolution microdisplay devices. It prefers being applied to the reflective liquid crystal on silicon microdisplays because of the pixel structure asymmetry and PMOS transistor switches used.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.288-293
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• 2001

This paper presents the water-hammer effect due to the rapid opening and closing of isolation valve and thruster valve in the spacecraft propulsion system. The single propellant feed system was modeled to investigate the maximum peak pressure due to the water-hammer effect. The test parameters are tank supply pressure, shape and throat length of orifice and line length. Kerosene was used as the inert simulant propellant liquid instead of hydrazine. As downstream line length after isolation valve increased from 1.5 to 2.5m, the maximum line-filling water-hammer peak pressure decreased, but the average time interval between peak pressures increased. The maximum line-filling water-hammer peak pressure with orifice was lower than without orifice, and the maximum line-filling water-hammer peak pressure with orifice at the back of isolation valve was lower than with orifice in front of isolation valve. Without orifice, the maximum water-hammer peak pressure due to the rapid opening and closing of the thruster valve was about 126% of tank supply pressure. With orifice, it decreased. As orifice throat length increased, it decreased. The maximum water-hammer peak pressure due to the rapid closing of the thruster valve with converging-diverging orifice was lower than normal orifice. It was found that the orifice as a means of pressure drop was very effective to reduce the water hammer peak pressure at the thruster valve. The results of this study can be used for the design of spacecraft liquid propulsion feed system.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
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• pp.159-162
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• 2008

발사체의 상단에 사용되는 여러 가지 싸이클의 특성을 조사한 뒤, 그 중 가스발생기 후연소 싸이클 엔진의 특성을 살펴보았다. 발사체 상단에 사용되는 엔진은 추진제와 싸이클의 특성상 연소압-확장비 다이어그램에서 크게 3그룹으로 나뉘어 진다. 영역 II에 위치한 케로신 엔진은 모두 가스발생기 후연소 싸이클 엔진으로서 높은 압력과 복잡한 구조를 하고 있다. 이 싸이클은 그 특성상 2개 이상의 펌프를 사용한다. 즉, 연료라인을 둘로 분기하여 보다 높은 압력이 요구되는 가스발생기 라인에는 2차 펌프를 두어 좀 더 가압을 하여 보다 효율적인 파워사용이 가능하다. 기본적으로 모든 산화제는 가스발생기를 지나 연소기로 향하기 때문에 2차 펌프의 필요성이 줄어들지만 여러가지 이유로 주펌프 이전에 부스터 펌프를 두어 주산화제 펌프의 부담을 덜어주는 경우가 많다. 폐쇄형 엔진은 그 특성상 엔진 비추력 효율이 개방형 엔진보다 상대적으로 높기 때문에 상단엔진에 적합하다.