• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.22 no.5
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• pp.92-107
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• 2023

Recently, along with the continuous increase in the supply of electric vehicles, electric vehicle fire accidents are also showing a rapidly increasing trend. Electric vehicle fires last for a long time compared to fires in internal combustion engine vehicles and have problems with the risk of secondary explosions and the generation of large amounts of smoke. In particular, electric vehicle fires in underground roads, which are semi-enclosed spaces, may amplify the problems of existing electric vehicle fires. On the other hand, there are no domestic response guidelines for electric vehicle fires occurring inside underground roads. Therefore, an awareness of fire accidents was confirmed through a survey of the general public, and electric vehicle fire characteristics and primary considerations were derived from stakeholders related to electric vehicle fires in underpasses. Through this, the guidelines for responding to electric vehicle fires on underground roads were established.

• Journal of the Korean Chemical Society
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• v.29 no.2
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• pp.80-87
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• 1985

Radiation damage in a single crystal of ammonium sulfate caused by ${\gamma}$-irradiation at room temperature has given rise to several paramagnetic centers. Electron spin resonance (ESR) spectra of crystal are obtained with the X-band EPR spectrometer at room temperature. An intense and isotropic peak of Gaussian shape at g = 2.0036 is assigned to $SO_3^-$, which shows power saturation effects. Angular dependence of spectra is studied for the rotations about three mutually perpendicular axes a, b and c. The g-values are obtained from the relative distances between isotropic peak of $SO_3^-$ and anisotropic peak of the species. Principal $g^-$values and direction cosines were calculated by diagonalizing the 3${\times}$3 matrix whose elements are the $g^-$values for each species. From the analysis of characteristic principal $g^-$values and direction cosines for ammonium sulfate single crystal, anisotropic peaks corresponding to $SO_4^-,\;SO_2^-$ and defect structure corresponding to electron excess type are identified.

• Journal of KIISE
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• v.44 no.2
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• pp.132-138
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• 2017

We design and implement a process-based fault recovery system to increase the reliability of new memory based computer systems. A rollback point is made at every context switch to which a process can rollback to upon a fault. In this study, a clone process of the original process, which we refer to as a P-process (Persistent-process), is created as a rollback point. Such a design minimizes losses when a fault does occur. Specifically, first, execution loss can be minimized as rollback points are created only at context switches, which bounds the lost execution. Second, as we make use of the COW (Copy-On-Write）mechanism, only those parts of the process memory state that are modified (in page units) are copied decreasing the overhead for creating the P-process. Our experimental results show that the overhead is approximately 5% in 8 out of 11 PARSEC benchmark workloads when P-process is created at every context switch time. Even for workloads that result in considerable overhead, we show that this overhead can be reduced by increasing the P-process generation interval.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.193.1-193.1
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• 2015

실리콘 (Si) 기판 위에 고품질의 갈륨질화물 (GaN) 박막을 성장시키기 위한 노력이 계속되고 있다. 실리콘 기판은 사파이어 기판 보다 경제적인 측면에서 유리하고, 실리콘 직접화 공정에 GaN 소자를 쉽게 접목 가능하다는 장점이 있다. GaN 박막은 2차원 전자 가스형성을 통한 고속소자, 직접 천이형 밴드갭을 이용한 발광소자 및 고전압 소자로써 활용 가능한 물질이다. 종래에는 Si(100) 및 Si(111) 기판 위에 GaN 박막 성장에 대한 연구가 주로 진행되었다. 하지만 대칭성과 격자 불일치도 등 결정학적 특성을 고려할 때 Si(100) 기판 위에 고품질의 GaN 박막을 성장시키는 것은 쉽지 않다. Si(111) 기판은 실리콘 소자 직접화 공정에 적합하지 못한 단점을 가지고 있다. 반면, 최근 Si(110) 기판 위에서 비등방적 변형 제어를 통한 고품질 GaN 박막 성장이 보고 되어 실리콘 집적 소자와 결합한 고전압 소자 및 고속소자 구현에 관한 연구가 진행되고 있다. 본 연구에서는 투과전자현미경 연구를 바탕으로 Si(110) 기판 위에 성장된 GaN의 미세구조에 관한 연구를 소개한다. 열팽창계수의 차이에 의한 GaN 박막 내 결함 생성을 줄이기 위하여 AlN 완충층이 사용되었다. GaN 박막을 암모니아 ($NH_3$) 유량이 다른 조건에서 성장시킴으로써 GaN 박막 미세구조의 암모니아 유량 의존성에 관한 연구를 진행하였다. GaN 박막에서 투과전자현미경 연구와 X-ray 회절 연구를 통하여 결함 거동 및 결정성을 확인하였다. $NH_3$ 유랑이 증가함에 따라 GaN의 성장 거동이 3차원에서 2차원으로 변화됨을 관찰하였다. 또한, 전위밀도의 증가도 확인되었다. $NH_3$ 유량이 낮은 경우 GaN 전위는 AlN와 GaN 경계에 주로 위치하고 GaN 표면 근처에는 전위밀도가 감소하였으나, $NH_3$ 유량이 높을 경우 GaN 박막 표면까지 전위가 관통됨을 확인하였다.

• Korean Journal of Materials Research
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• v.4 no.1
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• pp.31-36
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• 1994

The bonding behavior of $SiO_{2}$ thin film and glass during VCR head fabrication was investigated, varying the surface roughness of substrate and the sputtering parameter. Insufficient fillings of grooves In the $SiO_{2}$ film with glass was postulated to give rise to the generation of bubble in the glass. The surface roughness of $SiO_{2}$ film was found to depend on that of substrate. The lower the deposition rate, the smoother the surface of film. The bubble free glass after bonding could be obtained using substrate polished with 0.05$\mu\textrm{m}$ $Al_2O_3$ powder under the sputtering condition of 10% oxygen pressure.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.7
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• pp.1429-1434
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• 2017

In automatic defect detection problem for spectacle lenses, it is important to extract lens area accurately. Many existing detection methods fail to do it due to insufficient minute noise removal. In this paper, we propose an automatic defect detection method using Bresenham algorithm and adaptive binarization strategy. After usual average binarization, we apply Bresenham algorithm that has the power in extracting ellipse shape from image. Then, adaptive binarization strategy is applied to the critical minute noise removal inside the lens area. After noise removal, We can also compute the influence factor of the defect based on the fuzzy logic with two membership functions such as the size of the defect and the distance of the defect from the center of the lens. In experiment, our method successfully extracts defects in 10 out of 12 example images that include CHEMI, MID, HL, HM type lenses.

• Journal of Internet Computing and Services
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• v.10 no.1
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• pp.101-110
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• 2009

Multi-agent systems are mostly used to integrate the intelligent and distributed approaches to various systems for effective sharing of resources and dynamic system reconfigurations. Object replication is usually used to implement fault tolerance and solve the problem of unexpected failures to the system. This paper presents the intelligent multi-agent distributed platform based on the dynamic object group management and proposes an object search technique based on the proposed filtered k-means (Fk-means). We propose Fk-means for the search mechanism to find alternative objects in the event of object failures and transparently reconnect client to the object. The filtering range of Fk-means value is set only to include relevant objects within the group to perform the search method efficiently. The simulation result shows that the proposed mechanism provides fast and accurate search for the distributed object groups.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.239-245
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• 2006

Ultrasonic inspection method is more profitable than X-ray radiographic inspection in cost and effect of defect detection such as dis-bond, damage, and it does'nt need special constructions and can be possible real time inspection with safety. This report explains the experiment and analysis of ultrasonic property of solid propellant and the inspection methods of propellant/liner dis-bond by inside or outside inspection, and of propellnat micro crack by damage. At result, ultrasonics has big attenuation$(6\sim8db/cm)$ in solid propellant, and it. can be possiblle to detect the defect of propellant/liner dis-bond by inside or outside inspection. And also it can be possible to detect the propellant micro crack caused by damage by using ultrasonic attenuation.

• Tunnel and Underground Space
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• v.9 no.2
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• pp.114-130
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• 1999

It is very important to study on the structural behaviors of structurally damaged tunnel linings. A series of centrifuge model tests were performed in order to investigate different behaviors of tunnel linings. A 1/100-scaled aluminum horseshoe tunnel linings with a radius 5 cm, height 8 cm were buried in a depth with dry Joomunjin standard sand, the relative density of which was 86%. Such sectional forces as bending moments and thrusts along the tunnel circumference were measured by twelve strain gages. Earth pressures in soil mass and on the outside of lining model were estimated by pressure transducers, ground surface settlements at a center and edges by using LVDTs.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.32.2-32.2
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• 2011

반도체 생산공정에서 CMP (Chemical-mechanical planarization) 공정은 우수한 전기전도성 재료인 Cu의 사용과 다층구조의 소자를 형성하기 위해서 도입되었으며, 최근 소자의 집적도가 증가함에 따라 CMP 공정 비중은 점점 높아지고 있다. Cu CMP 공정에서 연마제인 슬러리는 금속 표면과의 물리적 화학적 반응을 동시에 사용하여 표면을 연마하게 되며, 연마특성을 향상시키기 위해 산화제, 부식방지제, 분산제 및 다양한 계면활성제가 첨가된다. 하지만 슬러리는 Cu 표면을 평탄화하는 동시에 오염입자, 유기오염물, 스크레치, 표면부식 등을 발생시키며 결과적으로 소자의 결함을 야기시킨다. 특히 부식방지제로 사용되는 BTA (Benzotriazole)은 Cu CMP 공정 중 Cu-BTA 형태로 표면에 흡착되어 오염원으로 작용하며 입자오염을 증가시시고 건조공정에서 물반점 등의 표면 결함을 발생시킨다. 이러한 문제점을 해결하기 위해 Cu 표면에서 식각과 부식반응을 최소화하며, 오염입자 제거 및 유기오염물을 효과적으로 제거하기 위한 Post-CMP 세정 공정과 세정액 개발이 요구된다. 본 연구에서는 오염입자 및 유기물 제거와 동시에 표면 거칠기와 부식현상을 제어할 수 있는 post Cu CMP 세정액을 개발 평가하였다. 오염입자 및 유기오염물을 제거하기 위해서 염기성 용액인 TMAH 사용하였으며, Cu 이온을 용해할 수 있는 Chelating agent와 표면 부식을 억제하는 부식 방지제를 사용하여 세정액을 합성하였다. 접촉각 측정과 FESEM(field Emission Scanning Electron Microscope) 분석을 통하여 CMP 공정에서 발생하는 유기오염물과 오염입자의 흡착과 제거를 확인하였으며 Cu 웨이퍼 세정 전후의 표면 거칠기의 변화와 식각량을 AFM(Atomic Force Microscope)과 4-point probe를 사용하여 각각 평가하였다. 또한 세정액 내에서의 연마입자의 zeta-potential을 측정 및 조절하여 세정력을 향상시켰다. 개발된 세정액과 Cu 표면에서의 화학반응 및 부식방지력은 potentiostat를 이용한 전기화학 분석법을 통해서 chelating agent와 부식방지제의 농도를 최적화 시켰다. 개발된 세정액을 적용함으로써 Cu-BTA 형태의 유기오염물과 오염입자들이 효과적으로 제거됨을 확인하였다.