• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.8
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• pp.711-717
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• 2012

During the conceptual design phase of a light sport aircraft, the wind tunnel tests were conducted to investigate the static stability of newly-designed configuration. The 1/5 scale-down wind tunnel model consisted of fuselage, main wing, vertical tail and horizontal tail. The main wing and tails were able to be attached or detached from the fuselage. The aerodynamic forces and moments acting on the 6 different configurations compounding each component were measured by using the internal balance system and their static stability derivatives were derived. With these experimental data, the baseline lift and drag characteristics as well as the effects of each component to the longitudinal, directional and lateral static stability were quantitatively analyzed.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.159-160
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• 2012

지난 30년 동안 플래시 메모리의 주류 역할을 하였던 부유 게이트 플래시 메모리는 40 nm 기술 노드 이하에서 셀간 간섭, 터널 산화막의 누설전류 등에 의한 오동작으로 기술적 한계를 맞게 되었다. 또한 기존의 비휘발성 메모리는 동작 시 높은 전압을 요구하므로 전력소비 측면에서도 취약한 단점이 있다. 그러나 이러한 문제점들을 기존의 Si기반의 소자기술이 아닌 새로운 재료나 공정을 통해서 해결하려는 연구가 최근 활발하게 진행되고 있다. 특히, 플래시 메모리의 중요한 구성요소의 하나인 터널 산화막은 메모리 소자의 크기가 줄어듦에 따라서 SiO2단층 구조로서는 7 nm 이하에서 stress induced leakage current (SILC), 직접 터널링 전류의 증가와 같은 많은 문제점들이 발생한다. 한편, 기존의 부유 게이트 타입의 메모리를 대신할 것으로 기대되는 전하 포획형 메모리는 쓰기/지우기 속도를 향상시킬 수 있으며 소자의 축소화에도 셀간 간섭이 일어나지 않으므로 부유 게이트 플래시 메모리를 대체할 수 있는 기술로 주목받고 있다. 특히, TBM (tunnel barrier engineered memory) 소자는 유전율이 큰 절연막을 적층하여 전계에 대한 터널 산화막의 민감도를 증가시키고, 적층된 물리적 두께의 증가에 의해 메모리의 데이터 유지 특성을 크게 개선시킬 수 있는 기술로 관심이 증가하고 있다. 본 연구에서는 Si3N4/Ta2O5를 적층시킨 staggered구조의 tunnel barrier를 제안하였고, Si기판 위에 tunnel layer로 Si3N4를 Low Pressure Chemical Vapor Deposition (LPCVD) 방법과 Ta2O5를 RF Sputtering 방법으로 각각 3/3 nm 증착한 후 e-beam evaporation을 이용하여 게이트 전극으로 Al을 150 nm 증착하여 MIS- capacitor구조의 메모리 소자를 제작하여 동작 특성을 평가하였다. 또한, Si3N4/Ta2O5 staggered tunnel barrier 형성 후의 후속 열처리에 따른 전기적 특성의 개선효과를 확인하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.184-184
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• 2011

반도체 전자 소자의 초고집적회로(VLSI, Very Large Scale Integrated Circuit)가 수년간 지속됨에 따라 실리콘 기반으로 하는 MOSFET 성능의 한계에 도달하게 되었다. 재료 물성, 축소, 소자 공정 등에 대한 원인으로 이를 극복하고자 하는 재료와 성능향상에 관한 연구가 진행되고 있다. 이에 기존 시스템의 전자의 전하 정보만을 응용하는 것이 아니라 전자의 스핀 정보까지 고려하는 스핀트로닉스 연구분야가 주목을 받고 있다. Spin-FET는 스핀 주입, 스핀 조절, 스핀측정 등으로 나뉘어 연구되고 있으며 이 중 스핀 주입의 효율 향상이 우선시 해결되어야 한다. 일반적으로 스핀 주입 과정에서 소스가 되는 강자성체와 스핀 확산 거리가 긴 반도체 물질과의 Conductance mismatch가 문제되고 있다. 이에 자성 반도체는 근본적인 문제를 해결하고 반도체와 자성체의 특성을 동시에 나타내는 물질로써, Si과 Ge (4족) 등의 반도체뿐만 아니라, GaAs, InP (3-5족), ZnO, ZnTe (2-6족) 등의 반도체 또한 많은 연구가 이루어지고 있다. 자성 반도체에서 해결해야 할 가장 큰 문제는 물질이 자성을 잃는 Curie 온도를 상온 이상으로 높이는 것이다. 이에 본 연구는 전이금속이 도핑된 4족 Si 반도체 박막을 성장하고 후처리 공정을 통하여 나타나는 구조적, 자기적 특성을 연구하였다. 펄스 레이저 증착 방법을 통하여 p-type Si 기판위에 전이금속 Fe이 도핑된 박막을 500 nm 로 성장하였다. 성장 온도는 $250^{\circ}C$로 하였고, 성장 분압은 $3 {\times}10^{-3}$Torr 로 유지하며 $N_2$ 가스를 사용하였다. 구조적 결과를 보기 위해 X선 회절 분석과 원자력 현미경 결과를 확인하였고, 자기적 특성을 확인하기 위해 저온에서 초전도 양자 간섭계로 조사하였다. XRD를 통해 (002)면, (004)면의 Si 기판 결정을 보았으며, Fe 관련된 이차상이 형성됨을 예측해 보았다. ($Fe_3Si$, $Fe_2Si$ 등) 초전도 양자 간섭계에서 20 K에서 측정한 이력 현상을 관찰하고, 온도변화에 따른 전체 자기모멘트를 관찰하였으며 이는 상온에서도 강자성 특성이 나타남을 확인하였다.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2010.04a
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• pp.201-206
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• 2010

A project for construction of Korea Geodetic VLBI has officially started in Oct. 2008. The construction of all system will be completed by the end of 2011. The project was named Korea VLBI system for Geodesy (KVG), and its main purpose is to maintain the Korea Geodetic Datum. In case of the KVG system, an observation room where an H-maser frequency standard is located is in a building separated from an antenna by several tens of meters. Therefore KVG system will adopt a so-called round-trip system to transmit reference signals to the antenna with diminishing the effect of path length variations. KVG's round-trip system is designed not only available to use either metal or optical fiber cables, but also available to measure path length variations directly by using K5/VSSP32 sampler. We will present principle of round-trip system and the new type of round trip system for KVG.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.6
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• pp.504-510
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• 2004

The objective of this paper is to propose the image interpolation method with pseudomedian filter for Field warping and morphing, and to evaluate and analyze its subjective image quality. The Field warping relatively gives rise to more computing overhead, but it can use the control line to control the warping result with more elaboration. Due to the working characteristics of the image warping and morphing process, various complex geometrical transformations occur and a image interpolation technique is needed to effectively process them. Of the various interpolation techniques, bilinear interpolation which shows above average performance is the most widely used. However, this technology has its limits in the reconstructivity of diagonal edges. The proposed interpolation method is to efficiently combine the bilinear interpolation and the pseudomedian filter-based interpolation which shows good performance in the reconstructivity of diagonal edges. According to the proposed interpolation method, we could get more natural warping and morphing results than other interpolation methods.

• Journal of Energy Engineering
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• v.26 no.4
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• pp.127-142
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• 2017

After individual consumption tax on bituminous coal has been imposed by Korean government after 2014 Jul, we analyse the influence of tax and conclude that the consumption of high calorie coal has been increased and that of low/middle calorie coal has been decreased. And also, the average calorie of coal consumption has been increased and the more fuel cost happens on account of the average calorie increase. Those effects have been caused by the current tax imposition system which does not reflect the bituminous coal trait. The motivation of oversea resource development and the effort of coal blending skill have been decreased because of the current tax policy. We suggest 2 ways of the tax policy improvement system[1. tax imposition system in proportion to 5,000kcal/kg, 2. 15 stages(1 stage : 200kcal/kg) segmentation tax imposition system equal to the tax/(5,000kcal/kg)] to increase the current tax amount, to prevent the coal consumption distortion and to remove the further fuel cost.

• Journal of the Korean housing association
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• v.17 no.2
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• pp.125-134
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• 2006

The tightness of windows have devoted to the improvement of thermal insulation and energy saving in buildings. But it is known that this tightness causes some side effects such as low ventilation, low capacity to humidity and temperature control and these are not profitable for inhabitants. To act on these side effects, Korean traditional windows which are composed of Han-Ji(Koreand traditional paper) and Chang-Sal(Korean traditional wooden frame) have been studied to get a reasonable solutions for these problems. In this study, to compare the thermal and humidity control performance of current window(12 mm pair) and Korean traditional windows, frames which are made of existing window and Korean traditional windows are adapted to scale model house and then humidity and temperature of in and out of scale model house are measured and analysed. The results of this study are followings ; 1) When Korean traditional window charges 20cm(1/8 of total window area) from total window area, Han-Ji window has higher thermal insulation than that of existing window in daytime. There is the most big thermal difference when double faced with double-ply Han-Ji window is placed to mock-up house. In night-time, the temperature difference is very small so this means that Korean traditional window is good to cover direct sunlight in daytime and reduce the temperature of balcony. One faced with one-ply han-Ji window has the best humidity penetration performance among three type of Korean traditional windows. 2) When Korean window area enlarged to 40cm(1/4 of total window area), the function of 40cm width Han-Ji window is higher than that of 20cm's. This means that enlargement of Han-Ji window cover direct sunlight more and is more efficient in humidity penetration.

• Journal of the Korea Institute of Building Construction
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• v.11 no.6
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• pp.609-617
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• 2011

For the past several decades, the residential housing market has been led by construction firms rather than consumers; in essence, it has been a suppliers' market. However, the market is experiencing a transition to a buyers' market, the implication of which is that there will be increased competition among the residential building suppliers. For this reason, it is necessary for construction firms to prepare new strategies to respond to the rapidly changing market environment. Furthermore, consumer satisfaction should be valued more highly than in the past, and should be a baseline in formulating construction product development strategy. For the pre-classified 13 apartment building segments, questionnaire surveys are conducted for the 50 CS (Customer Satisfaction) experts to evaluate their perceptions on the weighing of the quality of each apartment segment. Data obtained from a survey of experts was analyzed from an industry perspective utilizing the AHP technique. Analysis results indicate that the CS experts valued the kitchen & dining area more highly than all other segments. Specific analysis results and implications drawn from the study can be a valuable basis for marketing, product development, and quality management.

• The Journal of the Acoustical Society of Korea
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• v.21 no.5
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• pp.503-509
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• 2002

Cylindrical chamber silencers with an extended inlet and outlet are extensively used in many application fields to reduce the propagated noise in ducts. The basic attenuation effectiveness in the low frequency region can be explained by the reactive wave action inside the expansion chamber associated with the geometric configurations of the inlet and outlet locations, and the area expansion of the jacket. In this study. an acoustic analysis is carried out for a concentric extended pipe inserted into a simple expansion chamber. An algebraic equation is derived by using the eigenfunction expansion and orthogonality principle in which the acoustic pressures and particle velocities defined on each subdivided surface are expressed by the separable coordinates. By using the proposed analytical method, transmission losses are predicted for several configurations of the concentric extended systems and they agree very well with experimental results.

• Fire Science and Engineering
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• v.32 no.1
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• pp.66-75
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• 2018

A barrier installed within a rack plays a significant role in delaying the initial spread of fire but it can be an obstacle to a ceiling-type sprinkler installed for extinguishing fires and for supplying fire extinguishing water. An in-rack sprinkler and a barrier can be applied at the same time, but a study on a barrier's ability to delay fire spread or its effect on the in-rack sprinkler is needed. Accordingly, this study examined the effect of a barrier on the delay of fire spread and the in-rack sprinkler according to installation conditions through the reduced scale fire test. As a result, the delay in fire spread increased more than four times when a horizontal barrier and a vertical barrier were installed at the same time. The temperature was also increased two to three times with the compartment, resulting in the early operation of the in-rack sprinkler.