• KIEAE Journal
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• 제13권4호
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• pp.103-112
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• 2013

The Federal Democratic Republic of Nepal(Nepal) is one of the poorest country in the world. People in Nepal are having lots of housing problems including the lack of housing provision. Even Habitat for Humanity Nepal (HfH_Nepal) has developed various programs to diffuse ecological housing, still there are many problems due to financial and technological shortage. The purpose of this study is to verify the effects of suggestion of performance improvement for HfH_Nepal eco house with introduction of the housing situation and efforts to provide sustainable housing by HfH_Nepal in Terai plain. Ideas on CGI sheet roof with poor insulation, double panel bamboo wall and adobe brick wall which can overcome structural and waterproof flaws of the thin single panel bamboo wall. The experiment result shows that both ideas adapted to adobe brick house reduces daily temperature range 50.8% and humidity adjust effect. For the effective provision of adobe brick house, compressive strength was tested for the bricks made with locally available fiber materials. Brick with jute displayed 41.1% betterment than plain brick with closest packing condition while coconut and straw showed 25.1% and 7.9% improvement respectively. Technical and economic problems brought up during the building and experiment process were listed and countermeasures established. This kinds of building prototype houses and experiments can improve the living conditions of people in developing countries with little supplement of resources. Furthermore, consideration of locally available and affordable material can help the social and ecological sustainability in the world.

• JSTS:Journal of Semiconductor Technology and Science
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• 제15권5호
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• pp.490-496
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• 2015

We have grown AlN/GaN heterostructure which is a promising candidate for mm-wave applications. For the growth of the high quality very thin AlN barrier, indium was introduced as a surfactant at the growth temperature varied from 750 to $1070^{\circ}C$, which results in improving electrical properties of two-dimensional electron gas (2DEG). The heterostructure with barrier thickness of 7 nm grown at of $800^{\circ}C$ exhibited best Hall measurement results; such as sheet resistance of $215{\Omega}/{\Box}$electron mobility of $1430cm^2/V{\cdot}s$, and two-dimensional electron gas (2DEG) density of $2.04{\times}10^{13}/cm^2$. The high electron mobility transistor (HEMT) was fabricated on the grown heterostructure. The device with gate length of $0.2{\mu}m$ exhibited excellent DC and RF performances; such as maximum drain current of 937 mA/mm, maximum transconductance of 269 mS/mm, current gain cut-off frequency of 40 GHz, and maximum oscillation frequency of 80 GHz.

• 대한기계학회논문집B
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• 제20권10호
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• pp.3334-3343
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• 1996

A quantitative flow visualization technique was developed to measure velocity and temperature fields simultaneously in a two-dimensional cross section of thermo-fluid flows. Thermochromic liquid crystal(TLC) particles are used as temperature sensor and velocity tracers. Illuminating a thermo-fluid flow with a thin sheet of white light, the reflected colors from the TLC particles in the flow were captured simultaneously by two CCD cameras; a 3-chip CCD color camera for temperature field measurement and a black and white CCD camera for velocity field measurement. Variations of temperature field were measured by using a HSI true color image processing system and TLC solution. The relationship between the hue values of TLC color image and real temperature was obtained and this calibration curve was used to measure the true temperature under the same camera and illumination condition. The velocity field was obtained by using a 2-frame PTV technique using the concept of match-probability to track true velocity vectors from two consecutive image frames. These two techniques were applied at the same time to the unsteady thermal-fluid flow in a Hele-Shaw cell to measure the temperature and velocity field simultaneously and some results are discussed.

• 대한기계학회논문집A
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• 제34권6호
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• pp.797-803
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• 2010

자동차의 측면 충돌시 승객을 보호하고자 박판재를 이용하여 자동차의 도어 임팩트빔을 핫스탬핑공법을 이용하여 개발하였다. 핫스탬핑 기술은 차량의 차체 강성을 증가시킬 뿐만 아니라 차체 중량 및 부품 수 축소로 인한 공정의 감소도 가능하게 한다. 핫스탬핑 시편을 제작하고, 기계적 물성시험을 수행하여 물성 데이터를 확보하였다. 핫스탬핑 임팩트빔의 성형해석및 구조해석을 이용한 최적 설계를 수행하여 기존 파이프형태의 임팩트빔보다 강도는 102% 향상되고, 중량은 34% 감소된 핫스탬핑 임팩트빔을 개발하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제32권5호
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• pp.707-716
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• 2008

The objective of this study was to analyze the effect of mixed fuel composition and mass fraction on spray inner structure in evaporating transient spray under the variant ambient conditions. Spray structure and spatial distribution of liquid phase concentration were investigated using a thin laser sheet illumination technique on the three component mixed fuels. A pulsed Nd:YAG laser was used as a light source. The experiments were conducted in a constant volume vessel with optical access. Fuel was injected into the vessel with electronically controlled common rail injector. Used fuel contains i-octane($C_8H_{18}$), n-dodecane($C_{12}H_{26}$) and n-hexadecane($C_{16}H_{34}$) that were selected as low-, middle- and high-boiling point fuel, respectively. Experimental conditions are 42 MPa, 72 MPa and 112 MPa in injection pressure, $5\;kg/m^3$, $15kg/m^3$ and $30kg/m^3$ in ambient gas density, 300 K, 500 K, 600 K and 700 K in ambient gas temperature, 300 K and 368 K in fuel temperature and different fuel mass fraction. Experimental results indicated that the multi-component fuels made two phase region mixed vapor and liquid so that it would are helpful to improve combustion, for the fuels of high boiling point component could accelerate evaporation very much according as low boiling point fuel was added to high boiling point fuel.

• 한국표면공학회지
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• 제29권6호
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• pp.683-690
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• 1996

In this study, the diffusion barrier properties of $1000 \AA$ thick molybdenum compounds (Mo, Mo-N, $MoSi_2$, Mo-Si-N) were investigated using sheet resistance measurements, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), and Rutherford backscattering spectrometry (RBS). Each barrier material was deposited by the dc magnetron sputtering, and annealed at 300-$800^{\circ}C$ for 30min in vacuum. Mo and $MoSi_2$ barrier were failed at low temperature due to Cu diffusion through grain bound-aries and defects of Mo thin film and the reaction of Cu with Si within $MoSi_2$ respectively. A failure temperature could be raised to $650^{\circ}C$-30min in the Mo barrier system and to $700^{\circ}C$-30min in the Mo-silicide system by replacing Mo and $MoSi_2$ with Mo-N and Mo-Si-N, respectively. The crystallization temperature in the Mo-silicide film was raised by the addition of $N_2$. It is considered that not only the N, stuffing effect but also the variation of crystallization temperature affects the reaction of Cu with Si within Mo-silicide. It was found that Mo-Si-N is more effective barrier than Mo, $MoSi_2$, or Mo-N to copper penetration preventing Cu reaction with the substrate for 30min at a temperature higher than $650^{\circ}C$.

• 한국진공학회지
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• 제9권4호
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• pp.335-340
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• 2000

코발트실리사이드형성에 있어서 Capping layer로써의 Ti의 역할에 대한 연구를 수행하였다. 실리콘 산화막이 제거된 Si(100)기판과 $H_2SO_4$에 의한 chemical oxide를 형성한 Si(100)기판 위에 Co와 Ti를 증착한 후 열처리 온도 증가에 따른 계면반응과 상변화 등의 미세구조와 면저항 특성의 변화를 four point prove, XRD, TEM, SIMS등의 분석을 통하여 TiN capping, capping layer가 없는 경우에 대하여 비교하였다. 실리콘 산화막이 제거된 Si 기판 상에서 Ti capping의 경우 TiN capping, capping layer가 없는 경우보다 높은 온도에서 $CoSi_2$상이 형성되었으며, chemical oxide가 형성된 Si 기판 상에서는 Ti capping의 경우 코발트 실리사이드 박막을 형성 할 수 있었다. 이것은 capping layer인 Ti가 1차 RTA(Rapid Thermal Annealing)동안 Si 기판 방향으로 확산 침투하여 Co와 Si 사이에 존재하는 실리콘 산화막을 분해하는 역할을 하기 때문이다.

• 열처리공학회지
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• 제16권5호
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• pp.260-266
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• 2003

In order to study the interfacial reaction between Nb thin sheet and Fe-C-(Si) alloy with different Chemical compositions, they were cast-bonded. The growth of carbide layer formed at the interface after isothermal heat treatment at 1173K, 1223K, 1273K and 1323K for various times was investigated. The carbide formed at the interface was NbC and the thickness of NbC layer was increased linearly in proportional to the heat treating time. Therefore, It was found that the growth of NbC layer was controlled by the interfacial reaction. The growth rate constant of NbC layer was slightly increased with increase of carbon content when the silicon content is similar in the cast irons. However, as silicon content increases with no great difference in carbon content, the growth of NbC layer was greatly retarded. The calculated activation energy for the growth of NbC layer was varied in the range of 447.4~549.3 kJ/moI with the compositions of cast irons.

• 공업화학
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• 제20권6호
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• pp.612-616
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• 2009

Transparent conducting oxide (TCO) 박막은 평판 디스플레이 산업에 널리 사용되고 있다. 화학적으로 우수한 투명전도성 indium zinc oxide (IZO) 필름은 현재 널리 사용되고 있는 indium tin oxide (ITO) 필름의 대체 물질로 관심을 끌고있다. 본 연구에서는 ITO에 비해 낮은 증착 온도에서도 낮은 비저항과 높은 투과율을 가지는 IZO 박막을 전자빔 증착법을 사용하여 polynorbornene (PNB) 기판(Tg = $330^{\circ}C$) 위에 증착하는 조건에 대하여 연구하였다. 90 : 10 wt%의 $In_2O_3$와 ZnO를 혼합하여 만든 타겟으로 전자빔 증착법을 이용하여 PNB 기판 위에 IZO 박막을 제조하여, 기판온도와 산소도입 속도에 따른 IZO 필름의 전기 광학적 특성을 연구하였다. 그 결과 4 sccm의 $O_2$, $150^{\circ}C$의 기판온도, 증착속도 $2{\AA}$/sec 및 $1000{\AA}$ 두께로 증착된 IZO 필름에서 우수한 전기 광학적 성질인 $5.446{\times}10^2{\Omega}/{\boxempty}$ 면저항 및 87.4% 광투과율을 얻을 수 있었다.

• 한국정밀공학회지
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• 제16권4호통권97호
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• pp.57-63
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• 1999

A thin metal plate such as detent spring has the shape deformation due to the phenomenon of spring back after press machining and heat treatment process. This requires the correction of spring shape and force in final inspection process. To do correction of the shape deformation the impact force is manually applied to the bended part of detent spring after measuring the shape deformation and spring force. To develop the automatic spring force correction system, applied force of occurring plastic deformation must be derived from the experimental method. But frequent change of spring shape and material makes it difficult to accomplish the experimental method to be applied. This paper describes the analytical method for detent spring force correction system is to be substituted for the experimental method. FEM(Finite Element Method) is used to find the boundary value between elastic and plastic deformation in the analytical method. To confirm the validity of the analytical method, the result of two methods is compared each other at various applied force conditions. It shows that the simulation result of the analytical method is consistent with the result of the experimental method within the error bound ${\pm}$5%. The result of this paper is useful for development of the automatic spring correction system and reduction of the complicated and tedious processes involved in experimental method.