• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.527-530
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• 2010

A performance test of an air cycle machine with an air to air heat exchanger was performed. The air cycle machine designed for avionics cooling in a fighter's external pod is a small turbo machine operated on the reverse Brayton air cycle driven by captured ram air which is the source of driving energy and it can be used as cooling fluid going through electronics in the pod during the flight. The air to air heat exchanger was also used to avoid moisture for avionics. The performance test have verified that the developed ACM and heat exchanger meet the design requirements.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.4
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• pp.51-57
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• 1999

Temperature and velocity controlling of air at inlet position of Ramjet combustor is important under Ramjet engine grounding-test condition since temperature of inlet air increases due to compression process by supersonic flow at inlet position of Ramjet combustor. In this study, Vitiated Air Heater methodology was used to control temperature of air that is inducted into Ramjet combustor. Temperature and velocity of air at Vitiated air heater exit, which is inducted into Ramjet combustor, were measured to evaluate Vitiated air heater system developed in this study. It is shown that temperature and velocity of inducted air can be well controlled using Vitiated air heater system developed in this study, and we could make a Vitiated Air which is almost same with real air.

• Korean Journal of Breeding Science
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• v.40 no.3
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• pp.291-294
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• 2008

Amylogram properties such as peak viscosity, hot viscosity, cool viscosity, breakdown, pasting consistency and setback were investigated by the Rapid Visco Analyzer and interpreted by the relationship among amylogram properties according to the varietal groups classified by the rapidity of grain filling (RGF) which was calculated by the percentage of grain weight at 15 days after heading to 40 days after heading. The 164 rice recombinant inbred lines from the cross of Milyang23 and Gihobyeo were used to get the basic information regarding the amylogram properties. The used recombinant inbred lines could be grouped into 4 varietal groups such as slow maturing (less than 40% of RGF), mid-slow maturing (41-60% of RGF),mid-fast maturing (61-80% of RGF), and fast maturing (more than 81% of RGF) groups based on the RGF. The peak viscosity and setback showed regular tendency according to the varietal groups classified by the RGF. Positive significant correlations were found between pasting consistency and setback, however negative significant correlations were found between breakdown and setback in all varietal groups.

• The Optical Journal
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• s.145
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• pp.31-35
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• 2013

최근 자동차에 사용되는 조명은 LED가 주를 이루고 있다. 자동차 실내조명, 계기판 등에 사용되는 내부 조명의 경우 대부분 LED를 적용한 제품이며, 헤드램프, 후방 램프 및 방향 지시등과 같은 외부 조명의 경우도 LED로 교체되고 있다. 특히 LED 기반 헤드램프의 경우 과거 3500cc 이상 승용차 등에 한정되었으나 현재는 그 이하 레벨의 승용차 및 SUV 차량으로 범위가 빠르게 확산되고 있다. 고효율, 긴 수명 및 빠른 응답 속도가 장점인 LED를 차량용 조명 광원으로 사용함으로써 기존 할로겐램프나 HID 광원의 대체재로서의 전환이 활발히 이루어지고 있다. 할로겐램프의 경우 청색보다 적색 파장의 광량이 많은 관계로 황색에 가까운 백색을 보이며, HID 램프의 경우 할로겐램프보다는 백색 계열에 더 가깝다. 하지만 LED 램프는 파장의 순도가 높아 보다 완벽한 백색 구현이 가능하다. 또한 단순한 기능을 지닌 헤드램프에서 지능형 헤드램프로의 발전이 빠르게 이루어지고 있다. 이에 따른 LED의 수요 또한 증가할 것으로 예상된다. 향후 고효율 LED 소자의 개발과 함께 자동차용 LED 조명에 대한 적용은 급속도로 진행될 것으로 예상되며, 앞으로 자동차 조명 분야에서는 'LED 헤드램프/후미등 기술+IT 기술(센서+통신)'이 융합된 형태로 발전할 것이다. 본고에서는 LED 자동차 융합 기술 동향 및 전망에 대해 자세히 기술하였다.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.1
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• pp.41-49
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• 1998

A nonlinear mathematical model of longitudinal combustion instability appropriate for ramjets and augmenters was developed based on modal analysis. The model was limited to a two-mode formulation. The associated differential equations were solved both analytically and numerically. The two-mode nonlinear model is capable of predicting the bootstrapping effect which characterizes nonlinear velocity-sensitive combustion response. Also, parametric studies were performed.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.12
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• pp.13-21
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• 1996

In this paper, methods to reduce wire sweep during the chip-encapsulation process have been studide. Two methods have been tried for this purpose, namely runner balancing and ram velocity control. Runner balancing has been achieved automatically by using a computer program. Ram-velocity control has been achieved using empirical rules and results from a flow simulation of the encapsulation process. A mold which has 12 cavities for chip has been used as a case study. The simulation results show that the wire sweep obtained from the optimal process condition is about 1/5 of that from initial, unoptimized condition.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.274-277
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• 2004

Fuel/air mixing in air turbo ramjet(ATR) combustor is a significant parameter of combustion stability and efficiency. In this study, fuel distribution in the ATR model combustor was measured to compare the degree of mixing with respect to the velocity ratio$(r=v_a/v_f)$ between fuel gas and air. Planar laser-induced fluorescence(PLIF) and image processing method were used to obtain two dimensional fuel distribution. Fuel mixing went bad with approaching to r=1.

• The Journal of the Acoustical Society of Korea
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• v.25 no.3
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• pp.107-112
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• 2006

The elastic waves in a plate are dispersive waves due to the characteristics of Lamb waves. However, S0 symmetric mode is less dispersive in the frequency region below the first cut-off frequency. The wave Propagation velocities vary with the direction in anisotropic plates such as Carbon Fiber Reinforced Plastic (CFRP) Plates. The wave vector direction and energy flow vector direction are same in isotropic plates. However, the wave vector direction same as the phase velocity direction is not in accordance with the energy flow direction same as the group velocity direction in anisotropic plates. In this study. the dispersion curves or the phase velocity from anti-symmetric and symmetric Lamb wave dispersion equation are calculated for unidirectional laminated composite plate. Slowness surface is sketched using phase velocity under the first cut-off frequency. The direction and magnitude of group velocity are corrected with this slowness surface. The measured group velocities are in good agreement with the corrected group velocity curve except near the fiber direction zone which is called the cusp region.

• The KIPS Transactions:PartD
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• v.11D no.1
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• pp.11-22
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• 2004

As random access memory chip gets cheaper, it becomes affordable to realize main memory-based database systems. Consequently, reducing cache misses emerges as the most important issue in current main memory databases, in which CPU speeds have been increasing at 60% per year, compared to the memory speeds at 10% per you. In this paper, we design and implement a main-memory database system for real-time mobile GIS. Our system is composed of 5 modules： the interface manager provides the interface for PDA users； the memory data manager controls spatial and non-spatial data in main-memory using virtual memory techniques； the query manager processes spatial and non-spatial query : the index manager manages the MR-tree index for spatial data and the T-tree index for non-spatial index : the GIS server interface provides the interface with disk-based GIS. The MR-tree proposed propagates node splits upward only if one of the internal nodes on the insertion path has empty space. Thus, the internal nodes of the MR-tree are almost 100% full. Our experimental study shows that the two-dimensional MR-tree performs search up to 2.4 times faster than the ordinary R-tree. To use virtual memory techniques, the memory data manager uses page tables for spatial data, non- spatial data, T-tree and MR-tree. And, it uses indirect addressing techniques for fast reloading from disk.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.6
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• pp.21-31
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• 2017

In the present study, theoretical and numerical analyses have been carried out to investigate the detailed flow characteristics during the mode transition. The theoretical analysis rearranged the knowledge of gasdynamics and the previous studies, and the numerical analysis has conducted to solve the 2D unsteady compressible Navier-Stokes equations with a fully implicit finite volume scheme. To validate the numerical analysis, the experiment was compared with it. The total temperature at the inlet of isolator and the hydrogen fuel equivalent ratio were changed to investigate their effects on the mode transition phenomenon. As the results, the numerical analysis reproduced well the experiment qualitatively, the increment in the hydrogen fuel equivalent ratio induced the scram-mode to ram-mode transition which is discontinuous with a non-allowable region, and the variation in the total temperature changed the boundary of the mode transition.