• 대한기계학회논문집
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• 제13권1호
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• pp.115-124
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• 1989

본 연구에서는 2상계 스테인리스강의 모재,용접재 및 용접후 열처리재 3종류의 경우에 대하여 피로크랙 전파특성을 피로크랙의 하한계치 근방에서 금속조직적인 영향을 검토하기 위하여, 각 조건에 대한 피로크랙 전파속도의 하한 계치를 구하였고 피로식검후의 파단면을 주사전자현미경(SEM)으로 관찰하였다. 용접재에 대하여는 용착부 부근 용접열영향부의 입경측정, .alpha./.gamma.상의 체적비교율의 변화량 측정 및 용접재와 용접후열처리재의 잔유응력분포측정을 통하여 피로크랙의 하한계특성에 미치는 여러가지 영향인자에 대하여 검토하였다.

• 한국해양공학회지
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• 제11권3호
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• pp.39-47
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• 1997

Recently developed TMCP steels, which were manufactured by controlled rolling followed by accelerated cooling process, were examined to study their characteristics and weldability. Accelerated cooling type TMCP steel's hardness test result exhibited high value on weld zone. On the contrary, base metal and HAZ exhibited comparatively the similar value. On this experiment result Softening of HAZ is not occurred. in the-heat affected zone, grain size repression be caused by chemical composition properties which a small quantity Al-Ti-B-N. Changing stress ratio near-threshold fatigue crack propagation experiments were carried out. According to this result, crack propagation velocity of the HAZ exhibited slower than the base metal and near-threshold value had increased at the HAZ. Finally accelerated cooling type TMCP steels were exhibited excellent mechanical properties in both strength and toughness.

• 한국안전학회지
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• 제15권3호
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• pp.1-6
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• 2000

In fatigue crack growth test, it is important not only to analyze characteristics of fatigue crack growth but also to determine the threshold stress intensity factor, ${\Delta}K_{th}$. which is the threshold value of fatigue crack growth. Linear regression analysis using fatigue test data near the threshold is suggested to determine the ${\Delta}K_{th}$ in the standard test method but the ${\Delta}K_{th}$ can be affected by a fitting method. And there are some limitations on the linear regression analysis in the case of small number of test data near the threshold. The objective of this study is to investigate differences of the ${\Delta}K_{th}$ due to regression analysis method and to evaluate the relative error range of the ${\Delta}K_{th}$ in same fatigue crack growth test data.

• JSTS:Journal of Semiconductor Technology and Science
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• 제15권6호
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• pp.678-684
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• 2015

Near-threshold computing (NTC) is now regarded as a promising candidate for innovative power reduction, which cannot be achieved with conventional super-threshold computing (STC). However, performance degradation and vulnerability to process variation in the NTC regime are the primary concerns. In this paper, we propose a voltage- and frequency-tuning methodology for mitigating the process-variation-induced problems in NTC-based manycore architectures. To implement the proposed methodology, we build up multiple-voltage multiple-frequency (MVMF) islands and apply a voltage-frequency tuning algorithm based on the critical-path monitoring technique to reduce the effects of process variation and maximize energy efficiency in the post-silicon stage. Experimental results show that the proposed methodology reduces overall power consumption by 8.2-20.0%, compared to existing methods in variation-sensitive NTC environments.

• 한국전자통신학회논문지
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• 제11권2호
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• pp.159-164
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• 2016

무선통신시스템은 한정된 에너지를 갖는 배터리를 사용하기 때문에 저전력 회로로 구현되어야 하며, 이를 위하여 주파수와 상관없이 일정한 전력을 나타내는 전류모드 회로가 연구되어왔다. 본 논문에서는 초저전력 동작이 가능하도록 Dynamic Voltage Scaling 전원을 유도하며, 전류모드 신호처리 중 메모리 동작에서 저장된 에너지가 누설되는 Clock-Feedthrough 문제를 최소화하는 전류메모리 회로를 제안한다. $0.35{\mu}m$ 공정의 BSIM3 모델로 Near-threshold 영역의 전원 전압을 사용한 시뮬레이션을 진행한 결과, 1MHz의 스위칭 동작에서 $2{\mu}m$의 메모리 MOS Width, $0.3{\mu}m$의 스위치 MOS Width, $13{\mu}m$의 Dummy MOS Width로 설계할 때, Clock-Feedthrough의 영향을 최소화시킬 수 있었으며 1.2V의 Near-threshold 전원전압에서 소비전력은 $3.7{\mu}W$가 계산되었다.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.157-160
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• 2002

The dosage of intra-operative BNCT using near-threshold $^{7}$ Li(p,n)$^{7}$ Be direct neutrons was evaluated with the calculation method validated with the phantom experiment. The production of both neutrons by near-threshold $^{7}$ Li(p,n)$^{7}$ Be and gamma rays by $^{7}$ Li(p,p'gamma)$^{7}$ Li in a Li target was calculated using Lee's method and their transport in the phantom was calculated with MCNP-4B. As a result, the region satisfying the requirements of the protocol in intra-operative BNCT for brain tumors in Japan was acknowledged to be comparable to present BNCT, for the proton energy of 1.900 MeV for example. A boron-dose enhancer (BDE) introduced in this study to increase $^{10}$ (n,$\alpha$)$^{7}$ Li dose in a living body was effective. The void used to increase doses in deep regions was also valid with the BDE. It was found that intra-operative BNCT using near-threshold $^{7}$ Li(p,n)$^{7}$ Be direct neutrons is feasible.

• 열처리공학회지
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• 제3권2호
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• pp.37-44
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• 1990

The effect of the microstructural change on the near threshold fatigue crack growth rate in SM40C steel has been studied using the ${\Delta}K$ decreasing method. Below the total strain amplitude of 0.56%, cyclic softening occured, whereas above this value cyclic hardening occurred in the pearlitic lamellar structure. However, in the spherodized structure the cyclic hardening solely occurred. The crack growth rate in the near-threshold region was decreased with increasing prior austenite grain size and this was due to surface roughness. The crack growth rate of the spherodized structure was lower than that of the pearlite lamellar structure and the ${\Delta}K_{th}$ of the former was higher than that of the latter. It was understood that the crack propagates preferentially through the ferrite phase. The intergranular facets in the near-threshold region appeared in the spherodized structure.

• 대한물리치료과학회지
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• 제2권4호
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• pp.771-778
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• 1995

편광 근적외선 조사가 실험적 통증역치에 영향을 미치는지를 규명하기 위해서 건강한 성인의 합곡혈에 여러 단계의 출력량으로 편광 근적외선을 30초간 조사하고 시간 경과에 따라 실험적 통증역치를 측정하여 분석하였다. 실험 결과 출력량 0 %인 대조군과 10 % 및 20 %의 출력량에서는 실험적 통증역치의 유의한 변화가 없었다. 그러나 출력량 40 %군의 실험적 통증역치는 편광 근적외선 조사전 $3.85{\pm}0.51mA$에서 조사 직후 $4.77{\pm}0.87mA$, 조사 후 30분 $5.57{\pm}0.98mA$, 조사 후 1시간 $5.68{\pm}1.06mA$, 조사 후 2시간 $5.34{\pm}0.96mA$로 증가되었고, 출력량 80 %군에서도 실험적 통증역치가 조사전 $3.87{\pm}0.92mA$에서 조사 직후 $4.45{\pm}0.62mA$, 조사 후 30분 $4.91{\pm}0.51mA$, 조사 후 1시간 $4.93{\pm}0.62mA$, 조사 후 2시간 $5.55{\pm}1.11mA$로 증가하였다. 실험적 통증역치는 편광 근적외선 조사 직후부터 2시간까지 유의하게 증가하였다. 40 % 출력량과 80 % 출력량의 실험적 통증역치는 유의한 차이가 없었고, 출력량과 시간의 상호작용효과는 없었다. 건강인의 실험적 통증역치를 대상으로 한 본 연구 결과를 통증이 있는 환자에게 직접 적용하기는 어렵다고 생각하며 앞으로 환자를 대상으로한 연구가 수행되기를 기대한다.

• 열처리공학회지
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• 제10권4호
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• pp.266-277
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• 1997

Near-threshold fatigue crack growth characteristics was investigated on the Ni-Cr-Mo-V low alloy steel, which has the different microstructure obtained by tempering at various temperature. The specimens were austenized at $950^{\circ}C$ and then followed by tempering at $200^{\circ}C$, $530^{\circ}C$ and $600^{\circ}C$. Strain rate was obtained from strain gauge attached on the crack tip and crack opening point was observed through load-strain curve. Threshold stress intensity range(${\Delta}K_{th}$) was increased with increasing tempering tempuerature, but the effective threshold stress intensity rage (${\Delta}K_{eff,\;th}$) was not affected with the increasing temperature. Grain size increased with increasing tempering temperature.

• Journal of the Optical Society of Korea
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• 제20권3호
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• pp.407-412
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• 2016

We analyzed through numerical simulations the properties of a square beam homogenizer near the target for laser shock peening. The efficiency was calculated near the target by considering the plasma threshold of the metals. We defined the depth of focus of the square beam homogenizer with a given efficiency near the target. Then, we found the relationship between the depth of focus for the laser shock peening and four main parameters of the square beam homogenizer: the plasma threshold of the metal, the number of lenslets in the array-lens, the focal length of the condenser lens and the input beam size.