• 항공우주기술
• /
• 제1권2호
• /
• pp.113-122
• /
• 2002

3단형 과학로켓의 주엔진 추진제의 분사균일성에 대하여 수치해석을 수행하고 설계 개선안을 도출하였다. 분사기 유로는 동일한 압력강하를 가지는 다공성 매질로 처리하였다. 산화제와 연료 모두 공급 유로의 반대쪽에서 분사속도가 높은 것으로 예측되었으며 이는 유동정체에 따른 정압 상승에 기인한다. 산화제 매니폴드 내부의 수직분리판에 유로를 구성함으로써 매니폴드 중심과 외곽에서의 분사균일성을 향상시킬 수 있었다. 산화제 공급유로가 경사를 가지더라도 분사균일성과 압력손실에 미치는 영향은 거의 없었다. 또한 산화제/ 연료에 대한 분사속도로부터 혼합비의 분포를 예측하였다.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
• /
• pp.95-98
• /
• 2010

본 연구에서는 고농도 과산화수소와 케로신을 산화제와 연료로 사용하는 다중 인젝터 액체로켓엔진을 설계, 제작하였고 수류시험을 수행하였다. 이 엔진에는 6개의 동축 선회형 인젝터를 사용하였으며, 유동해석 결과를 바탕으로 정체 구간과 재순환 영역을 최소화한 매니폴드 유로를 설계, 제작하였다. 최종적으로 수류실험을 통해 추진제의 공급 유량 및 분무 성능을 확인하였으며, 인젝터의 설계 타당성을 검증하였다.

• 한국수소및신에너지학회논문집
• /
• 제27권2호
• /
• pp.220-229
• /
• 2016

A numerical study on lifted flame structure in impinging jet geometry with syngas composition ratio was investigated. The numerical calculations including chemical kinetic analysis were conducted using SPIN application of the CHEMKIN Package with Davis-Mechanism. The flame temperature and velocity profiles were calculated at the steady state for one-dimensional stagnation flow geometry. Syngas mixture compositions were adjusted such as $H_2:CO=10:90(10P)$, 20 : 80 (20P), 30 : 70 (30P), 40 : 60 (40P), 50 : 50 (50P). As composition ratios are changed from 10P to 50P, the axial velocity and flame temperature increase because the contents of hydrogen that have faster burning velocity increase. This phenomenon is due to increase in good reactive radicals such as H, OH radical. As a result of active reactivity, the burning velocity is more faster and this is confirmed by numerical methods. Consequently, combustion reaction zone was moved to burner nozzle.

• 한국건설관리학회:학술대회논문집
• /
• 한국건설관리학회 2007년도 정기학술발표대회 논문집
• /
• pp.674-677
• /
• 2007

최근 국내 건설시장은 내수시장의 침체와 포화상태로 인해 위기를 겪고 있다. 이와 같은 위기를 기회로 수많은 건설업체들은 해외로 눈길을 돌리고 있다. 이미 1965년 이후 해외진출은 시작되었지만, 현재까지의 진출 특성을 살펴보면, 플랜트에 치우친 공사수주와 정부의 근시안적인 전략 마련으로 인해 장기적인 시장 확보가 불가능한 상태이다. 본 논문은 이와 같은 국내건설업체의 해외건설시장 진출 특성을 분석하여 문제점을 도출하고, 이 문제점을 해결하기 위해 SWOT 분석을 통하여 새로운 전략을 제안하고자 한다.

• 동의생리병리학회지
• /
• 제25권1호
• /
• pp.149-153
• /
• 2011

In this study, we structuralized the diagnostic indices used for pattern identification (PI) of stroke, and suggested an AHP method to obtain the weights of PI indices. AHP of the subjects under consistency ratio 0.1 showed that the critical indices for stroke PI consists of 9 for Qi-deficiency, 13 for Phlegm/dampness, 7 for blood stagnation, 12 for Yin-deficiency and 16 for Fire/heat. Furthermore, AHP analysis rendered the weights of indices of each PI that will be useful for oriental medical experts to perform objective PI.

• 전기학회논문지
• /
• 제58권9호
• /
• pp.1658-1666
• /
• 2009

This paper proposes an approach of Mult_HPSO based on the PC cluster system to reduce or remove the stagnation on an early convergence effect of PSO, reduce an execution time and improve a search ability on an optimal solution. Hybrid PSO(HPSO) is combines the PSO(Particle Swarm Optimization) with the mutation of conventional GA(Genetic Algorithm). The conventional PSO has operated a search process in a single swarm. However, Multi_PSO operates a search process through multiple swarms, which increments diversity of expected solutions and reduces the execution time. Multiple Swarms are composed of unsynchronized PC clusters. We apply to SCED(security constrained economic dispatch) problem, a nonlinear optimization problem, which considers line flow constraints and N-1 line contingency constraints. To consider N-1 line contingency in power system, we have chosen critical line contingency through a process of Screening and Selection based on PI(performace Index). We have applied to IEEE 118 bus system for verifying a usefulness of the proposed approaches.

• 한국조경학회지
• /
• 제29권6호
• /
• pp.27-36
• /
• 2002

The objective of this study is to improve the quality of the atmospheric environment by incorporating the factors of meteorology and urban climate into the field of urban and environmental planning. To this end, we have conducted a study on CLIMATOP and the mapping of urban climate, which are basic data used to analyze changes in climatic factors and the stagnation and accumulation of air pollutants. In particular, we focused on understanding the formation and movement of cold fresh air and its influx into urban areas by measuring and analyzing climatic factors. As a study result, classification criteria far CLIMATOP and a urban climatic map were made. In addition, we analyzed a digital elevation model, climatic data, and isothermal curves. As a result, we identified the corridor through which cold fresh air moves. We also observed that the temperature of the fluxed cold fresh air increased as land use changed. When the results of this study are applied to urban re-development and re-building projects, which require preliminary environmental assessment and environmental impact assessment, the practice proposed by this study is expected to contribute to the natural purification of air pollution activating the movement of cold fresh air and its influx into urban areas.

• 한국농촌건축학회논문집
• /
• 제10권2호
• /
• pp.27-36
• /
• 2008

This study is progressing or suggests effective space planning for rural village area conventional markets that is planning business market modernization process. Rural village area conventional markets of small scale are inputting a lot of efforts and financial resources for activation. Also, I wish to quote activation plan for rural village area conventional markets that face in stagnation. Studied spatial form and conventional market activation factors by space use special quality of rural village area conventional markets for architectural planning plan presentation. Investigated spatial change for several years that appear in Geum-wang conventional market for this. As a result, could deduce plans of space improvement plan for conventional market space positively. Also, through this study, suggest activation plan of conventional market that display similar space type including Geum-wang conventional market. Therefore, environment improvement of conventional market's type and special quality based on space activation elements and need space environment improvement plan the architecture plan in early planning phase of business.

• 한국시스템다이내믹스연구
• /
• 제10권4호
• /
• pp.5-25
• /
• 2009

Since the end of the 1950-1953 Korean War, many scholars and policymakers have expressed concern about the possibility of another conflict on the peninsula. In certain respects, the post-1953 North-South Korea relationship resembles the Cold War that existed between the United States and the Soviet Union, 1945-1990. Although a "hot" never occurred, peace was never guaranteed. By looking at international theories (i.e., realism and liberal theory) and by utilizing casual-loop diagram analysis, the main purpose of this research is to explore on the likelihood of peace and war on the Korean peninsula. First, several factors (e.g., economic stagnation of North Korea, unstable political systems, and so on) emphasized by realism perspectives are significantly related to the likelihood of conflict between North and South Korea. Conversely, several determinants (e.g., economic assistance to North Korea, inter-dialogue between two Koreas, cultural and social exchange, and so on) emphasized by liberal approaches are significantly related to likelihood of peace on the Korean peninsula. Given the two different interpretations about the likelihood of conflict or peace, it can be argued that a second military action might occur on the Korean peninsula if realism theories are true. However, if practical factors exist on the Korean peninsula, the two Korean can optimistically expect a peaceful reunification in the future, without interference from other countries.

• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1993년도 추계학술대회
• /
• pp.104-106
• /
• 1993

Some cardio-vascular assist systems need more inexpensive artificial heart valves for short-term use. To meet with this need, we have developed a new polymer valve that is very simple to manufacture and of which its dimensions are easy to change, depending on its application. We have tested the hydrodynamic performance of the new polymer valve using a mock circulatory testing system and studied the flow through the valve using high-speed camera combined with image processing techniques. The results show that this valve is superior in its performances to the other valves (Bjork-Shiley mechanical valve and trileaflet polymer valve) and have no stagnation points. We also have tested the hemolytic potential of the valve. The valve is less hemolytic than the Bjork-shiley mechanical valve finally, we have applied this valve to a left ventricular assist device that we are developing.