• Journal of Astronomy and Space Sciences
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• v.26 no.4
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• pp.693-702
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• 2009

A computational fluid analysis was performed on an LOx line system of a liquid rocket engine. The model was created with 3D CAD and imbedded to the 3D CFD program. Before the full scale analysis on the system was carried out, each components with simplified models was analyzed to save time and cost. As a result, the inlet pressure of the gas generator should be compensated with a certain device unless the inlet pressure of the line system is sufficiently high. The flow pattern of the exit of the system was dependant upon the location of the orifice as well as the size. As a whole the line system analyzed met the requirements, and will be tested and confirmed after being manufactured.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.553-556
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• 2009

In this study, ignition tests of a gas turbine combustor were performed to evaluate an ignition loop at low temperature condition. An experimental setup was constructed to simulate low temperature condition with a heat exchanger using dry ice as a coolant. Various low temperature conditions could be created by controlling the amount of air though the heat exchanger. The results showed that ignition limit decreased with air temperature.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.35-36
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• 2005

An ejector driven by a liquid is a fluid transfer equipment to be used under a poor suction condition, which means that there exists a possibility to occur a cavitation. It is a highly reliable device because it has no movable part in it, that is only a passive equipment. The ejector is an inevitably necessary one to overcome a poor pumping condition and to mix uniformly two fluids, however it has a low efficiency since it requires a pump for its operation. This study is for the development of a new-type liquid ejector with the application of a nozzle shape alteration, which maximize the suction performance of it. which provides the increased competition with the domestic industries. Also, the increased performance opens a new manufacturing method to use a commercial pipes for the production of an ejector, which is based on a trivial loss of a performance. However, this minor loss can be sufficiently compensated by the increased performance of a new-type ejector. Therefore, the developed ejector by this study can considerably reduce the manufacturing time and cost while its performance is largely increased.

• Journal of Welding and Joining
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• v.32 no.3
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• pp.89-94
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• 2014

AISI 304 austenitic stainless steel is widely used for LNG pipes for LNG transmission thanks to its good metallurgical and mechanical properties. In the present research, impact toughness of a gas tungsten arc welded AISI 304 stainless steel pipe was evaluated between room and liquid nitrogen ($-196^{\circ}C$) test temperatures. In addition, a comparative study was made of the fracture behavior of FCC crystal structured stainless steel weldments and BCC crystal structured mild steels(A-grade and SS400). The results showed a slight decrease in the impact energy of the AISI 304 base metal, heat affected zone(HAZ), and welded zone with decreasing test temperature. In addition, the welded metal has the highest absorbed impact energy, followed by HAZ and the base metal.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.43 no.4 s.310
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• pp.30-34
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• 2006

To enhance the performance of the piezoelectric transducer for the transit-time type ultrasonic sensors, we investigated and verified the effect of it's size and raw materials using FEM(Finite Element Method) technique. Radiation angle of $25^{\circ}$ could be realized through the control of the matching layer's shape and its raw materials. Based on the results, the flowmeter is fabricated and characterized in real application, which thereby proves good sensitivity of 10 times better than current commercial one.

• Proceedings of the Korean Society of Computer Information Conference
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• 2016.01a
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• pp.87-90
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• 2016

현재 한국 군부대에서 사용되고 있는 표적구동장치는 1990년도에 만들어진 재래식 장비로서 노후화 및 부품교체 난제로 인하여 지속적인 시스템의 오류와 이에 따른 장비 가동률 저하 등의 문제로 실전적인 사격 훈련이 어렵다. 이에 본 연구에서는 보다 효과적인 훈련을 진행하고자 복합 구동 표적장치를 개발하였다. 본 연구에서 개발된 복합 구동 표적장치는 Up-down, Swing, Turn, Rotary 방식의 표적 구동을 원격으로 제어하여 다양한 사격 및 전술 훈련 적용 가능하도록 제작되었으며, 또한 사격진행 통제 결과를 통제관 혼자서 총괄 운용이 가능한 모니터링 시스템을 구축하였다. 그리고 현재 각 부대에 설치되어 있는 표적구동장치 및 전술훈련 컨트롤러는 유선을 통한 시리얼통신 및 중앙 분배식 전원공급시스템으로서 운영설비를 위하여 과도한 배관배선 등의 공사가 별도로 시행되어야 하는 문제점이 있다. 따라서 본 연구에서는 이러한 문제점을 해결할 수 있도록 무선 통신시스템방식을 적용하여 다양한 훈련지역에 호환 적용될 수 있는 장비를 개발함으로써 훈련장 시설건립을 위한 부담을 줄이고, 운영의 극대화를 확보할 수 있도록 경제적, 기술적 효과를 추구하였다.

• 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.

• Journal of Sensor Science and Technology
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• v.12 no.3
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• pp.139-148
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• 2003

$LiPO_3$ glass scintillators were fabricated, and lanthanides(except Pm) oxides or chlorides were used as an activator. For the fabrication of $LiPO_3$ glasses, optimum heating conditions were obtained, and the photoluminescence of the glasses was measured by the monochromator. For the best transparency of the glass samples, optimum heating temperature and time are $950^{\circ}C$ and 90 min, respectively. It was found that Pr, Nd, Gd, Ho, Er, Tm, Yb and Lu do not work as activator; emission spectrums of samples with them were equal to those of samples without activators. In the case of samples with Europium, the peaks of emission spectrum of $Eu^{2+}$ and $Eu^{3+}$ were 420 nm and 620 nm respectively. And samples with $Ce^{3+}$ were about 380 nm, and $Tb^{3+}$ were about 550 nm. Glass scintillators with $Be^{3+}$, $Eu^{2+}$, and $Ce^{3+}$ were found to be more applicable to neutron detection. The result of neutron detection by Ra-Be sources showed that $Ce^{3+}$ was found to be the best activator of $LiPO_3$.

• Journal of Astronomy and Space Sciences
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• v.19 no.4
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• pp.305-318
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• 2002

We have constructed two flight models of airglow photometer system (AGP) to be onboard Korea Sounding Rocket-III (KSR-III) for detection of MUV dayglow above the Korean peninsular. The AGP system is designed to detect dayglow emissions of OI 2972${\AA}$, $N_2$ VK(0,6) 2780${\AA}$, $N_2$ 2PG 3150${\AA}$ and background 3070${\AA}$ toward the horizon at altitudes between 100 km and 300 km. The AGP system consists of a photometer body, a baffle an electronic control unit and a battery unit. The MUV dayglow emissions enter through a narrow band interference filter and focusing lens of the photometer, which contains an ultraviolet sensitive photomultiplier tube. The photometer is equipped with an in-flight calibration light source on a circular plane that will rotate at the rocket's apogee. A bane tube is installed at the entry of the photometer in order to block strong scattering lights from the lower atmosphere. We have carried out laboratory measurements of sensitivity and in-flight calibration light source for the AGP flight models. Although absolute sensitivities of the AGP flight models could not be determined in the country, relative sensitivities among channels are well measured so that observation data during rocket flight in the future can be analyzed with confidence.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.2
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• pp.213-218
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• 2010

A cooling system utilizing liquid helium to chill the cryopanel (800 mm $\times$ 700 mm dimensions) down to 4.2 K was designed, implemented, and tested to verify the role of the cryopanel as a heat sink for the payload of a spacecraft inside the large thermal vacuum chamber (effective dimensions : 8 m ($\Phi$) $\times$ 10 m (L)) of KARI (Korea Aerospace Research Institute). Two LHe (Liquid Helium) Dewars, one for the main supply and the other for refilling, were used to supply liquid helium or cold helium gas into this cryopanel, and flow control for the target temperature of the cryopanel within requirements was done through fine adjustment of the pressure inside the LHe Dewars. The return helium gas from the cryopanel was reused as a thermal barrier to minimize the heat influx on the core liquid helium supply pipe. The test verified a cooling time of around three hours from the ambient temperature to 40 K (combined standard uncertainty of 194 mK), the capacity for maintaining the cryopanel at intermediate temperatures, and a 1 K uniformity over the entire cryopanel surface at around 40 K with 20 W cooling power.