• 비파괴검사학회지
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• 제7권1호
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• pp.32-41
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• 1987

As a new device of stress monitoring method, ultrasonic backscattering method has been used to aluminium samples with various grain sizes at rayleigh critical angle in order to observe the relationships between applied stress and ultrasonic backscattered energy. It was found that the ultrasonic backscattered energy was observed to decrease as the grain size increased at the given applied stress. At the same grain size, the ule ultrasonic backscattered energy increased with increasing the applies stress. Through this study, we provided some possibility to evaluate stresses in materials under loads nondestructively, and this method is expected to be used as a new stress monitoring device.

• 한국정밀공학회지
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• 제25권11호
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• pp.100-106
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• 2008

We have studied the characteristic changes of optical device using imprint lithography. An imprinted structure is inherently involved in residual stress due to the temperature and the pressure cycle during fabrication process. A structure with residual stress undergoes stress relaxation, which leads io dimensional change. Therefore, annealing processes was performed to reduce the residual stress of imprinted polymer channel. Reduction of residual stress was confirmed through dimensional change, birefringence, and the mechanical properties. We have fabricated an optical device, and it saw the optical intensity changes within 0.1% for 1 month.

• 대한전자공학회논문지
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• 제25권2호
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• pp.182-187
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• 1988

Hot carrier induced device degradation characteristics under DC bias stress have been investigated in n-MOSFETs with channel length of 1.2,1.8 um, and compared with those of LDD structure device with same channel length. Based on these results, the device lifetime in normal operating bias(Vgs=Vds=5V) is evaluated. The lifetimes of conventional and LDD n-MOSFET with channel length of 1.2 um are estimated about for 17 days and for 12 years, respectively. The degradation rate of LDD n-MOSFET under the same stress is the lowest at n-region implnatation dose of 2.5E15 cm-\ulcorner while the substrate current is the lowest at the dose of 1E13cm-\ulcorner Thses results show that the device degradation characteristics are basic measurement parameter to find optimum process conditions in LDD devices and evaluate a reliability of sub-micron device.

• 한국전기전자재료학회논문지
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• 제27권12호
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• pp.792-796
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• 2014

In this paper, we investigated the hot carrier reliability of two kinds of device with low threshold voltage (LVT) and regular threshold voltage (RVT) in 65 nm CMOS technology. Contrary to the previous report that devices beyond $0.18{\mu}m$ CMOS technology is dominated by channel hot carrier(CHC) stress rather than drain avalanche hot carrier(DAHC) stress, both of LVT and RVT devices showed that their degradation is dominated by DAHC stress. It is also shown that in case of LVT devices, contribution of interface trap generation to the device degradation is greater under DAHC stress than CHC stress, while there is little difference for RVT devices.

• Advances in biomechanics and applications
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• 제1권1호
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• pp.23-40
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• 2014

This paper examines the blood chamber of a left ventricular assist device (LVAD) under static loading conditions and standard operating temperatures. The LVAD's walls are made of a temperature-sensitive polymer (ChronoFlex C 55D) and are covered with a titanium nitride (TiN) nano-coating (deposited by laser ablation) to improve their haemocompatibility. A loss of cohesion may be observed near the coating-substrate boundary. Therefore, a micro-scale stress-strain analysis of the multilayered blood chamber was conducted with FE (finite element) code. The multi-scale model included a macro-model of the LVAD's blood chamber and a micro-model of the TiN coating. The theories of non-linear elasticity and elasto-plasticity were applied. The formulated problems were solved with a finite element method. The micro-scale problem was solved for a representative volume element (RVE). This micro-model accounted for the residual stress, a material model of the TiN coating, the stress results under loading pressures, the thickness of the TiN coating and the wave parameters of the TiN surface. The numerical results (displacements and strains) were experimentally validated using digital image correlation (DIC) during static blood pressure deformations. The maximum strain and stress were determined at static pressure steps in a macro-scale FE simulation. The strain and stress were also computed at the same loading conditions in a micro-scale FE simulation.

• 한국통신학회논문지
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• 제35권1A호
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• pp.80-86
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• 2010

본 논문은 게이트 채널 길이 0.13 [${\mu}m$]의 p-MOS 트랜지스터에서 음 바이어스 온도 불안정(NBTI) 전류 스트레스 인가에 의한 게이트유기 드레인 누설(GIDL) 전류를 측정 분석하였다. NBTI 스트레스에 의한 문턱전압의 변화와 문턱전압아래 기울기와 드레인 전류 사이에 상관관계로부터, 소자의 특성 변화의 결과로 열화에 대한 중요한 메카니즘이 계면 상태의 생성과 관련이 있다는 것을 분석하였다. GIDL 전류의 측정 결과로부터, NBTI 스트레스에 기인한 계면상태에서 전자-정공 쌍의 생성이 GIDL 전류의 증가의 결과를 도출하였다. 이런 결과로 부터, 초박막 게이트 산화막 소자에서 NBTI 스트레스 후에 증가된 GIDL 전류를 고려해야만 한다. 또한, 동시에 신뢰성 특성과 직류 소자 성능의 고려가 나노 크기의 CMOS 통신회로 설계의 스트레스 파라미터들에서 반드시 있어야 한다.

• Transactions on Electrical and Electronic Materials
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• 제2권3호
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• pp.12-17
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• 2001

It is shown in the present study that during the HTS (hot temperature storage) test, the metal contamination by impure elements can be highly susceptible to the void formation, leading to the open failure of the power line in the memory device. Such a functional failure associated with the metal contamination was investigated to be dominant in the early stages of the HTS test while the formation of a stress-driven void is mainly observed in the later stages. In particular, it was found that the void formed in the contaminated metal takes on a slit-like shape which has been known to be characteristic of the stress-related voiding. The impure elements leading to the metal degradation were identified to be carbon and oxygen introduced during the metal sputtering process. The experimental works show that the device reliability was significantly improved by reducing the level of such impure elements within metal. It is shown in the present study that during the HTS (hot temperature storage) test, the metal contamination by impure elements can be highly susceptible to the void formation, leading to the open failure of the power line in the memory device. Such a functional failure associated with the metal contamination was investigated to be dominant in the early stages of the HTS test while the formation of a stress-driven void is mainly observed in the later stages. In particular, it was found that the void formed in the contaminated metal takes on a slit-like shape which has been known to be characteristic of the stress-related voiding. The impure elements leading to the metal degradation were identified to be carbon and oxygen introduced during the metal sputtering process. The experimental works show that the device reliability was significantly improved by reducing the level of such impure elements within metal.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(2)
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• pp.5-8
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• 2002

Hot carrier induced device degradation is observed in thin-film, gate-all-around SOI transistor under DC stress conductions. We observed the more significant device degradation in GAA device than general single gate SOI device due to the degradation of edge transistor. Therefore, it is expected that the maximum available supply voltage of GAA transistor is lower than that o( bulk MOSFET or single gale SOI device.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.88-91
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• 2002

The two dimensional size effect of specimen gauge section (length x width) was investigated on the compressive behavior of a T300/924 [45/-45/0/90]3s, carbon fiber-epoxy laminate. A modified ICSTM compression test fixture was used together with an anti-buckling device to test 3mm thick specimens with a 30$\times$30, 50$\times$50, 70$\times$70, and 90mm$\times$90mm gauge length by width section. In all cases failure was sudden and occurred mainly within the gauge length. Post failure examination suggests that $0^{\circ}$ fiber microbuckling is the critical damage mechanism that causes final failure. This is the matrix dominated failure mode and its triggering depends very much on initial fiber waviness. It is suggested that manufacturing process and quality may play a significant role in determining the compressive strength. When the anti-buckling device was used on specimens, it was showed that the compressive strength with the device was slightly greater than that without the device due to surface friction between the specimen and the device by pretoque in bolts of the device. In the analysis result on influence of the anti-buckling device using the finite element method, it was found that the compressive strength with the anti-buckling device by loaded bolts was about 7% higher than actual compressive strength. Additionally, compressive tests on specimen with an open hole were performed. The local stress concentration arising from the hole dominates the strength of the laminate rather than the stresses in the bulk of the material. It is observed that the remote failure stress decreases with increasing hole size and specimen width but is generally well above the value one might predict from the elastic stress concentration factor. This suggests that the material is not ideally brittle and some stress relief occurs around the hole. X-ray radiography reveals that damage in the form of fiber microbuckling and delamination initiates at the edge of the hole at approximately 80% of the failure load and extends stably under increasing load before becoming unstable at a critical length of 2-3mm (depends on specimen geometry). This damage growth and failure are analysed by a linear cohesive zone model. Using the independently measured laminate parameters of unnotched compressive strength and in-plane fracture toughness the model predicts successfully the notched strength as a function of hole size and width.

• 대한조선학회논문집
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• 제61권5호
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• pp.389-399
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• 2024

Currently, shipyards are using ship block supports to hold various pre-erection (PE) blocks during ship construction work. The height adjustment method of the ship block support is performed by workers hammering and driving the wedge part, which requires repetitive high-load work. Accordingly, there are concerns about musculoskeletal diseases and safety accidents. To prevent safety accidents and improve work efficiency, this study developed a block support height adjustment device using a hydraulic cylinder. It was designed considering the ease of movement of the block support height adjustment device and the ease of adjusting the height of the block support by workers within the shipyard. Numerical analysis was conducted to confirm the critical points of the structural members of the designed block support height adjustment device and to verify the safety of the stress-based structure. As a result of the analysis, it was confirmed that the stress occurring at the critical point of the structural member was lower than the design allowable stress, making it structurally safe. Afterwards, the block support height adjustment device was redesigned for lightweight, and after verification of structural safety through numerical analysis, a prototype was manufactured and performance evaluation was conducted.