• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.392-392
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• 2010

In this study, high-speed chemical dry thinning process of Si wafer and evolution of surface roughness were investigated. Direct injection of NO gas into the reactor during the supply of F radicals from $NF_3$ remote plasmas was very effective in increasing the Si thinning rate due to the NO-induced enhancement of surface reaction but thinned Si surface became roughened significantly. Addition of Ar gas, together with NO gas, decreased root mean square (RMS) surface roughness of thinned Si wafer significantly. The process regime for the thinning rate enhancement with reduced surface roughness was extended at higher Ar gas flow rate. Si wafer thinning rate as high as $22.8\;{\mu}m/min$ and root-mean-squared (RMS) surface roughness as small as 0.75 nm could be obtained. It is expected that high-speed chemical dry thinning process has possibility of application to ultra-thin Si wafer thinning with no mechanical damage.

• Structural Engineering and Mechanics
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• 제47권4호
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• pp.575-598
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• 2013

The study presents the results of an experimental program concerning the shear force transfer between reinforced concrete (RC) jackets and existing columns with damages. In order to investigate the effectiveness of the repair method applied and the contribution of each shear transfer mechanism of the interface. It includes 22 concrete columns (core) (of 24,37MPa concrete strength) with square section (150mm side, 500 mm height and scale 1:2). Ten columns had initial construction damages and twelve were subjected to initial axial load. Sixteen columns have full jacketing at all four faces with 80mm thickness (of 31,7MPa concrete strength) and contain longitudinal bars (of 500MPa nominal strength) and closed stirrups spaced at 25mm, 50mm or 100mm (of 220MPa nominal strength). Fourteen of them contain dowels at the interface between old and new concrete. All columns were subjected to repeated (pseudo-seismic) axial compression with increasing deformation cycles up to failure with or without jacketing. Two load patterns were selected to examine the difference of the behavior of columns. The effects of the initial damages, of the reinforcement of the interface (dowels) and of the confinement generated by the stirrups are investigated through axial- deformation (slip) diagrams and the energy absorbed diagrams. The results indicate that the initial damages affect the total behavior of the column and the capacity of the interface to shear mechanisms and to slip: a) the maximum bearing load of old column is decreased affecting at the same time the loading capacity of the jacketed element, b) suitable repair of initially damaged specimens increases the capacity of the jacketed column to transfer load through the interface.

• 한국세라믹학회지
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• 제40권8호
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• pp.784-790
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• 2003

본 논문은 세라믹재료가 강화재로써 보강된 복합재료가 횡방향의 단축인장하중을 받는 경우, 복합재료의 변형, 재료내 발생되는 손상의 특징, 및 응력-변형률 특성에 관한 컴퓨터 해석결과이다. 해석은 SiC/Ti 시스템을 대상으로 하였으며, 특성은 강화재의 배열형태, 강화재/기지 계면에서의 결합유무, 강화재의 부피분율변화에 대하여 각기 해석되었다. 계면에서 강한 결합이 있는 복합재와는 달리, 약한 결합의 복합재는 인장하중에 의하여 세라믹/기지 계면에서 분리가 발생되었다. 이 분리는 전체 복합재의 강성을 감소시키며, 세라믹 강화재의 부피분율이 증가할수록 탄성계수 및 횡방향 평균응력의 최종크기를 나타내는 한계응력의 크기감소로 나타났다. 계면결합이 강한 경우는 세라믹 부피분율이 증가할수록 사각형 배열보다는 육각형배열의 복합재에서 다소 큰 증가율로 나타났다. 그러나, 계면결합이 약한 경우는 세라믹 부피분율이 증가할수록 사각형 배열보다는 육각형배열의 복합재에서 상대적으로 큰 감소율로 해석되었다. 본 연구의 해석결과는 알려진 문헌의 결과와 잘 일치하였다.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제4권5호
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• pp.171-176
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• 2015

특정 보안 기술만으로는 나날이 치밀해지는 공격을 방어할 수 없기 때문에 ISMS(Information Security Management System) 등 다양한 보안관리 모델 등이 적용되고 있지만, 너무 많은 항목에 대한 일반적인 보안관리 방안을 제시하고 있어 취약점이 높은 부분에 집중하지 못하는 단점이 있다. 최근 수년간 우리 사회에 막대한 피해를 입힌 주요 정보 및 기밀 유출 관련 사건을 분석한 결과, 공격자는 주로 이메일, 웹 서버, 휴대용 저장매체, 외주업체 직원 등 조직의 내부와 외부를 연결해주는 통로인 '인터페이스(interface)' 취약점을 이용하였음을 발견하였다. 이를 통해 우리는 보안에 투자해야 할 시간과 자원이 제한되는 현실을 고려하여 공격자가 악용할 가능성이 높은 인터페이스에 대한 현재 보안 실태를 적시한 후 관리적 기술적 물리적 측면을 융합한 보안대책을 제시하고, 해당 인터페이스에 대한 중점적이고 지속적인 관리(continuous management)를 통해 투자 비용 대비 효과적으로 조직의 실시간 보안관리를 가능하게 하는 체계를 제안하고자 한다.

• Structural Engineering and Mechanics
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• 제89권6호
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• pp.557-570
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• 2024

Due to interfacial ageing, chemical action and interfacial damage, the interface debonding may appear in the interfaces of composite laminates. Particularly, the laminates display a side-dependent effect at small scale. In this work, a three-dimensional (3D) and anisotropic thick nanoplate model is proposed to investigate the effects of imperfect interface and nonlocal parameter on the bending deformation, vibrational response and buckling stability of one-dimensional (1D) hexagonal quasicrystal (QC) layered nanoplates. By combining the linear spring model with the transferring matrix method, exact solutions of phonon and phason displacements, phonon and phason stresses of bending deformation, the natural frequencies of vibration and the critical buckling loads of 1D hexagonal QC layered nanoplates are derived with imperfect interfaces and nonlocal effects. Numerical examples are illustrated to demonstrate the effects of the imperfect interface parameter, aspect ratio, thickness, nonlocal parameter, and stacking sequence on the bending deformation, the vibrational response and the critical buckling load of 1D hexagonal QC layered nanoplate. The results indicate that both the interface debonding and nonlocal effect can reduce the stiffness and stability of layered nanoplates. Increasing thickness of QC coatings can enhance the stability of sandwich nanoplates with the perfect interfaces, while it can reduce first and then enhance the stability of sandwich nanoplates with the imperfect interfaces. The biaxial compression easily results in an instability of the QC layered nanoplates compared to uniaxial compression. QC material is suitable for surface layers in layered structures. The mechanical behavior of QC layered nanoplates can be optimized by imposing imperfect interfaces and controlling the stacking sequence artificially. The present solutions are helpful for the various numerical methods, thin nanoplate theories and the optimal design of QC nano-composites in engineering practice with interfacial debonding.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.395-400
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• 2004

For the purpose of monitoring by ultrasonic test of the ball bearing conditions in rotating machinery, a system for their diagnosis was developed. ultrasonic technique is used to detect abnormal conditions in the bearing system. And various data such as frequency spectrum, energy and amplitude of ultrasonic signals, and ultrasonic parameters were acquired during experiments with the simulated ball bearing system. Based on the above results and practical application for power plant, algorithms and judgement criteria for diagnosis system was established. Bearing diagnosis system is composed of four parts as follows : sensing part for ultrasonic sensor and preamplifier, signal processing part for measuring frequency spectrum, energy and amplitude, interface part for connecting ultrasonic signal to PC using A/D converter, graphic display and software part for display of bearing condition and for managing of diagnosis program.

• International Journal of Automotive Technology
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• 제1권2호
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• pp.71-77
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• 2000

High temperature materials in service are subjected to mechanical damage due to operating load and metallurgical damage due to operating temperature. Therefore, when designing or assessing life of high temperature components, both factors must be considered. In this paper, the effect of tensile hold time on high temperature fatigue crack growth and long term prior thermal aging heat treatment on creep rupture behavior were investigated using STS 316L and STS 316 austenitic stainless steels, which are widely used for high temperature components like in automotive exhaust and piping systems. In high temperature fatigue crack growth tests using STS 316L, as tensile hold time increased, crack growth rate decreased in relatively short tensile hold time region. In long term aged specimens, cavity type microcracks have been observed at the interface of grain boundary and coarsened carbide.

• Computers and Concrete
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• 제9권3호
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• pp.171-178
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• 2012

This paper presents numerical studies of stiff fiber pullout behaviors of fiber reinforced cementitious composites based on a progressive damage model. The ongoing debonding process is simulated. Interfacial stress distribution for different load levels is analyzed. A parametric study, including bond strength and the homogeneity index on the pullout behaviors is carried out. The numerical results indicate that the bond stress decreases gradually from loaded end to embedded end along fiber-cement interface. The debonding initially starts from loaded end and propagates to embedded end as load increasing. The embedded length and bond strength affect the load-loaded end displacement curves significantly. The numerical results have a general agreement with the experimental investigation.

• 대한기계학회논문집A
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• 제26권5호
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• pp.835-842
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• 2002

In this paper, static and fatigue bending strengths and failure mechanisms of CFRP (carbon fiber reinforced plastics) laminates having impact damages have been evaluated. Composite laminates used for this experiment are CF/EPOXY orthotropy laminated plates, which have two-interfaces $[0^0_ 4/90^0_4]_{ sym}$. A steel ball launched by the air gun collides against CFRP laminates to generate impact damages. The damage growth during bending fatigue test is observed by the scanning acoustic microscope (SAM) and also, the fracture surfaces were observed by using the SEM (scanning electron microscope). In the case of impacted-side compression, fracture is propagated from the transverse crack generated near impact point. On the other hand, fracture is developed toward the impact point from the edge of interface-B delamination in the case of impacted-side tension. Eventually, failure mechanisms have been confirmed based on the observed delamination areas and fracture surfaces.

• 한국전산구조공학회논문집
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• 제22권2호
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• pp.153-161
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• 2009

재료 비선형성을 갖는 열탄점소성 손상 문제와 경계 비선형성을 갖는 접촉 문제의 효율적인 해석을 위하여 열탄성 부영역, 열탄점소성/손상 부영역, 공유면, 접촉 공유면에 기반을 둔 영역/경계 분할법을 제안하였다. 대변형과 같은 지하학적 비선형성은 고려하지 않았으며, 영역 및 경계 분할에 관련된 공유면 및 접촉 공유면에서의 연속 구속 조건을 처리하기 위하여 간단한 벌칙 함수 기법을 적용하였다. 결과적으로 재료 및 경계 비선형성은 소수의 부영역과 접촉 경계면에서 계산되는 유한요소 행렬들에 국한된다. 따라서 적절한 해석 알고리듬을 구성하면 대폭적인 효율성 향상이 가능하게 된다. 간단한 수치 실험을 통해서 열탄점소성 손상 및 접촉 해석의 효율성에 관련된 기본적인 특성을 분석하였다.