• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.109-114
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• 2008

This paper presents the development status of a subscale precooled turbojet engine "S-engine" for the hypersonic cruiser and space place. S-engine employs the precooled-cycle using liquid hydrogen as fuel and coolant. It has $23cm{\times}23cm$ of rectangular cross section, 2.6 m of the overall length and about 100 kg of the target weight employing composite materials for a variable-geometry rectangular air-intake and nozzle. The design thrust and specific impulse at sea-level-static(SLS) are 1.2 kN and 2,000 sec respectively. After the system design and component tests, a prototype engine made of metal was manufactured and provided for the system firing test using gaseous hydrogen in March 2007. The core engine performance could be verified in this test. The second firing test using liquid hydrogen was conducted in October 2007. The engine, fuel supplying system and control system for the next flight test were used in this test. We verified the engine start-up sequence, compressor-turbine matching and performance of system and components. A flight test of S-engine is to be conducted by the Balloon-based Operation Vehicle(BOV) at Taiki town in Hokkaido in October 2008. The vehicle is about 5 m in length, 0.55 m in diameter and 500 kg in weight. The vehicle is dropped from an altitude of 40 km by a high-altitude observation balloon. After 40 second free-fall, the vehicle pulls up and S-engine operates for 60 seconds up to Mach 2. High altitude tests of the engine components corresponding to the BOV flight condition are also conducted.

• 항공우주정책ㆍ법학회지
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• 제9권
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• pp.445-488
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• 1997

In the forthcoming 21st century new technical and scientific developments in outer space demands new approaches towards the problems arising in several fields of the use and exploitation of outer space including practical applications. The main purposes of this study are to analyze the legal problems of geostationary orbital position, telecommunication, direct television broadcasting by uses of artificial satellites. Communication via artificial Earth satellites was one of the first applications of space technology and is now one of the most developed field. From the technical and economic standpoints the advantages of world-wide satellites communication system are too all obvious. However, as the practical uses of space technology become more freguent, the legal conflicts among nations have become more divisive. One of the problem grown in uses of artificial satellites is that of the increasing shortage of suitable orbital slot positions for satellites, especially in geostationary orbit. Legal status of geostationary orbit as a limited resourece have to be reviewed in consideration of the side effect of the "First use, first-served" principle. The geostationary orbit is to be used for the benifits of all mankind and to be guaranteed for each state institutionaly in order to have eguitable access to the use of the orbit. Rapid increase of satellites broadcasting system in not only developed countries but also in developing countries opened up new possibilities with one another's scientific and cultural achievements. But there is also a potential danger that this powerful new instrument of influencing public opinion will be abused. Such a danger incudes spill-over or harmful interference. This controversial issue brings about the question whether prior consent from the receiver nation is needed to broadcast across international boundaries. Some states have rejected prior consent because it interfere with the free flow of information. Many other countries have opposed that opinion as an invasion and violation of sovereignty and as a violation of the 1967 Treaty and the UN Charter. Since declaration of the First Year of Outer Space in 1985, our country have promoted the plan of launching communication and broadcasting satellites. With the Koreasat launched in 1995 as the start, a real satellite-telecommunication era was opened in korea. According to this new development of our country, there will also rise various legal problems related to satellite broadcasting and telecommunication such as the inflow of foreign programs, the permeation of culture and the infringement of program copyright. Consequently the effective reactions to these problems in satellite-communication era should be tried including international cooperation. It is therefore to take into careful consideration the legal issues which may arise in outer space activities and to formulate positive policy on international cooperation with surrounding or advanced countries and international organization concerned. For this purpose the United Nations also prepares the UNISPACE III in 1999, to enable the international community to meet a more promising 21st century.

• Journal of Advanced Marine Engineering and Technology
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• 제35권6호
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• pp.849-855
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• 2011

구명정은 선박이 좌초나 침몰 시 인명구조용으로 구조는 황천시 물이 구명정내부로 들어오지 못하도록 밀폐형으로 되어 있다. 밀폐형 구조로 인해 구명정내부는 온도가 상승되고 이 온도 상승으로 인해 엔진시동용 배터리가 폭발 가능성이 있고, 실제로 목포해대 실습선의 구명정에 탑재된 배터리에서 폭발사고가 발생했다. 폭발에 대한 원인조사를 바탕으로 폭발방지를 위한 대안 연구를 수행하였다. 본 연구에서는 발생된 사고의 방지를 위한 구명정의 구조개선, 충전장치, 법규개정을 위한 기초적 자료를 제안하였다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2005년도 제31회 KOSCO SYMPOSIUM 논문집
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• pp.58-63
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• 2005

As fuel cells approach commercialization, hydrogen production becomes a critical step in the overall energy conversion pathway. Reforming is a process that produces a hydrogen-rich gas from hydrocarbon fuels. Hydrogen production via autothermal reforming (ATR) is particularly attractive for applications that demand a quick start-up and response time in a compact size. However, further research is required to optimize the performance of autothermal reformers and accurate models of reactor performance must be developed and validated. The design includes the requirement of accommodating a wide range of experimental set ups. Factors considered in the design of the reformer are capability to use multiple fuels, ability to vary stoichiometry, precise temperature and pressure control, implementation of enhancement methods, capability to implement variable catalyst positions and catalyst arrangement, ability to monitor and change reactant mixing, and proper implementation of data acquisition. A model of the system was first developed in order to calculate flowrates, heating, space velocity, and other important parameters needed to select the hardware that comprises the reformer. Predicted performance will be compared to actual data once the reformer construction is completed. This comparison will quantify the accuracy of the model and should point to areas where further model development is required. The end result will be a research tool that allows engineers to optimize hydrogen production via autothermal reformation.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 춘계학술대회 논문집
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• pp.7-10
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• 2009

우주발사체용 액체추진제 로켓엔진을 시동할 때 사용되는 터보펌프 시동기에 적용하고자 고체추진제 개발 및 특성 평가를 수행하였다. 터보펌프 시동기용 추진제의 배출가스는 기계적인 부식 또는 대기오염 등의 이유로 화염온도가 낮아야 하고 고체입자 잔사 및 독성이 적은 것이 바람직하며, 작동시간이 어느 정도 유지가 되어야 하기 때문에 비교적 낮은 연소속도가 필요하다. 본 연구에서는 PCP계열의 바인더를 사용하고 oxygen balance나 점화성에서 유리한 DHG(Dihydroxy glyoxime)을 냉각제를 사용하는 추진제 조성을 개발하여 연소속도와 기계적 물성 등의 특성평가를 실시하였으며, 최종적으로는 지상연소시험을 통하여 터보펌프 시동기의 성공적인 개발 가능성을 입증하였다.

• Korea-Australia Rheology Journal
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• 제21권1호
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• pp.47-58
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• 2009

We have investigated the transient behavior of 1D fully developed Poiseuille viscoelastic flow under finite pressure gradient described by the Oldroyd-B and Leonov constitutive equations. For analysis we employ a simple $2^{nd}$ order discretization scheme such as central difference for space and the Crank-Nicolson for time approximation. For the analysis of the Oldroyd-B model, we also apply the analytical solution, which is obtained again in this work in terms of elementary solution procedure simpler than the previous one (Waters and King, 1970). Both models demonstrate qualitatively similar solutions, but their eventual steady flowrate exhibits noticeable difference due to the absence or presence of shear thinning behavior. In the inertialess flow, the flowrate instantaneously attains a large value corresponding to the Newtonian creeping flow and then decreases to its steady value when the applied pressure gradient is low. However with finite liquid density the flow field shows severe fluctuation even accompanying reversals of flow directions. As the assigned pressure gradient increases, the flowrate achieves its steady value significantly higher than its value during oscillations after quite long period of time. We have also illustrated comparison between 1D and 2D results and possible mechanism of complex 2D flow rearrangement employing a previous solution of [mite element computation. In addition, we discuss some mathematical points regarding missing boundary conditions in 2D modeling due to the change of the type of differential equations when varying from inertialess to inertial flow.

• 대한기계학회논문집B
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• 제26권11호
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• pp.1630-1637
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• 2002

A slab-wick heat pipe was fabricated and tested for applications where the condenser temperature is in a range of 80 to 12$0^{\circ}C$. The pipe material was 9.53 mm O.D. copper tube and the working fluids were ethanol and water. The total length of the heat pipe was 1.6 m, in which evaporator section was 1.4 m and the condenser was 0.10 m. The slab was a composite wick structure fabricated with STS316 wire screens. Thermal load was varied for a specified fill charge ratio and inclined angle. The optimum fill charge ratio was identified to be 110% based on a theoretical calculation of the pore space in the slab wick of the heat pipe. The maximum thermal load was 120W for ethanol and the same was 200W for water with the condenser temperature of 8$0^{\circ}C$. The thermal performance of the slab wick heat pipe is analysed in terms of temperature characteristics and thermal resistance against thermal load, tilt angle and fill charge ratio.

• Journal of East-Asian Urban History
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• 제1권
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• pp.135-154
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• 2019

This paper reveals the influence of urban and social contexts on the early building layout of Japan Women's College (JWC), one of the first women's colleges in Japan. According to the unpublished plans, the main building and other major structures, at the first stage, formed a three-sided quadrangle with site-wide organization, which was similar to contemporary National colleges. This impressive design, however, disappeared in the final plan. Although the school is the largest in student number and in campus ground size compared to other contemporary private colleges at its establishment, the subdivided land acquired in the private land market forced JWC to give up the organic composition of buildings. Under the framework of donation-based finance, it needed to start construction quickly for further support from the public, which prevented the school from acquiring enough time to adjust land ownership. These constitute the major differences with national schools. The founder's emphasis on the physical exercises, which reflected the public interest in physical strength of mothers in the time of wars, gave preference to securing sufficient open space over the order of buildings.

• Journal of Mechanical Science and Technology
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• 제20권6호
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• pp.864-873
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• 2006

As fuel cells approach commercialization, hydrogen production becomes a critical step in the overall energy conversion pathway. Reforming is a process that produces a hydrogen-rich gas from hydrocarbon fuels. Hydrogen production via autothermal reforming (ATR) is particularly attractive for applications that demand a quick start-up and response time in a compact size. However, further research is required to optimize the performance of autothermal reformers and accurate models of reactor performance must be developed and validated. The design includes the requirement of accommodating a wide range of experimental set ups. Factors considered in the design of the reformer are capability to use multiple fuels, ability to vary stoichiometry, precise temperature and pressure control, implementation of enhancement methods, capability to implement variable catalyst positions and catalyst arrangement, ability to monitor and change reactant mixing, and proper implementation of data acquisition. A model of the system was first developed in order to calculate flowrates, heating, space velocity, and other important parameters needed to select the hardware that comprises the reformer. Predicted performance will be compared to actual data once the reformer construction is completed. This comparison will quantify the accuracy of the model and should point to areas where further model development is required. The end result will be a research tool that allows engineers to optimize hydrogen production via autothermal reformation.

• 한국환경과학회지
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• 제30권3호
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• pp.267-277
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• 2021

This study investigates sound, scenery, and soundscape preferences, which are sensory factors that users feel in a healing forest, comparing the difference in recovery by the soundscape. In the barrier-free, wooden walking path of the National Daegwallyeong Healing Forest, a survey site with five different conditions was selected. Users prefer water sounds the most and places with open views for scenery. For the complex sensation of soundscapes, the most preferred is a space where water sounds can be heard, and either a waterfall or an open view can be seen. A profile of mood states test was use to compare users' psychological recovery by the soundscape. It was found that users felt the most positive mood with water sounds and open views. In addition, users' preference for artificial sounds, scenery, and soundscape was the lowest. In the mood state test, it was found that the artificial soundscape incited the most negative emotions.