• 마이크로전자및패키징학회지
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• 제15권4호
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• pp.77-86
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• 2008

본 연구에서는 유연솔더인 63Sn37Pb와 무연 솔더인 95.5Sn4.0Ag0.5Cu와 97Sn2.5Ag0.5Cu BGA(Ball Grid Array) 패키지를 인쇄회로기판(Printed Circuit Board, PCB)에 위치에 따라 장착하고 보드레벨의 낙하시험(Board Level Drop Test)을 실시하여 충격에 대한 유 무연 솔더의 특성을 분석하였고 4점굽힘시험(board Level 4-point Bending Test)을 실시하여 굽힘에 대한 솔더볼의 기계적 저항특성을 분석하였다. 또한 유한요소법(Finite Element Modeling, FEM)을 이용해 낙하시험과 4점굽힘시험에서 솔더 조인트에 미치는 응력과 변형률을 해석하였으며, 시험 설계 시에 솔더 조인트의 응력변화에 영향을 미칠 수 있는 변수를 고려하여 해석하고 결과를 비교 분석하였다. 낙하시험과 4점굽힘시험에서 모두 무연솔더는 유연솔더보다 2배 이상 높은 신뢰성을 보였으며, PCB의 중앙에 위치한 패키지는 외각에 위치한 패키지 보다 매우 낮은 신뢰성을 보였다. 유한요소법을 통해 해석한 결과 최외각 솔더에서 가장 큰 응력이 발생하였고, 솔더의 조성과, 시험설계변수에 의해 응력의 발생 정도가 다름을 나타내었다.

• Structural Engineering and Mechanics
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• 제75권3호
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• pp.401-414
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• 2020

Unlike the existing truss models for shear and torsion analysis, in this study, the torsional capacities of reinforced concrete (RC) members were estimated by introducing multi-potential capacity criteria that considered the aggregate interlock, concrete crushing, and spalling of concrete cover. The smeared truss model based on the fixed-angle theory was utilized to obtain the torsional behavior of reinforced concrete member, and the multi-potential capacity criteria were then applied to draw the capacity of the member. In addition, to avoid any iterative calculation in the existing torsional behavior model, a simple strength model was suggested that considers key variables, such as the effective thickness of torsional member, principal stress angle, and strain effect that reduces the resistance of concrete due to large longitudinal tensile strain. The proposed multi-potential capacity concept and the simple strength model were verified by comparing with test results collected from the literature. The study found that the multi-potential capacity could estimate in a rational manner not only the torsional strength but also the failure mode of RC members subjected to torsional moment, by reflecting the reinforcing index in both transverse and longitudinal directions, as well as the sectional and material properties of RC members.

• 소음진동
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• 제11권3호
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• pp.410-415
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• 2001

This paper describes an experimental analysis for improving the stability of blade failure due to the vibration resonance, which happens in the low-pressure steam turbine. Some cracks due to high cycle fatigue were found in the blades of a low-pressure turbine after long time operation. Impact test showed that such failure was mainly caused by the resonance. In other words, since one of the natural frequencies of the grouped blade is very close to the excitation frequency of the nozzle, the resonant vibration leads to a large amplitude of displacement and results in a large amount of stress that may cause fatigue failures in the blades. It is interesting that the blade failures occur only at blades neighboring with the nodal points of the natural vibration mode whose natural frequency is close to the nozzle passing frequency. The effective methods for increasing the reliability against the blade vibration are a heightening the fatigue limit of the blade using an advanced material and a removing the resonance away from the operating speed. It is well known that the removal of theresonance could be obtained by the installation of different types of shrouds, wires, and links between the blades as well as by the chance of the number of nozzles. In the present work, two kinds of modification for avoiding the resonance haute been considered; 1) slot-type finger, 2) long span cover. Full-scale mockup tests have been performed in order to confirm the verification for modification in the shop. Test results show that the use of long span cover is very useful to change the natural frequencies of the grouped blade and to avoid the resonance effectively.

• 전기전자학회논문지
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• 제19권2호
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• pp.265-270
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• 2015

본 논문에서는 높은 홀딩 전압을 갖는 SCR(silicon-controlled rectifier)기반 양 방향성 ESD 보호회로를 제안하였다. 일반적인 ESD 보호회로와 달리 양방향의 ESD Stress mode의 방전경로를 제공하며 높은 홀딩전압으로 latch-up면역 특성을 갖어 효과적인 ESD보호를 제공한다. 또한, 높은 홀딩전압을 위한 설계변수인 Gate Length와 N+bridge Length의 길이 변화에 따른 시뮬레이션을 Synopsys사의 TCAD 시뮬레이터를 사용하여 확인 하였다. 시뮬레이션 결과 2.1V에서 6.5V까지 홀딩 전압의 증가로 latch-up 면역 특성을 개선 하였으며, 기존 SCR보다 6.5V의 낮은 트리거 전압특성을 갖고 있어 제안된 ESD 보호 회로는 5V 이상의 공급전압을 갖는 application에 적용 가능하다.

• Journal of Electrical Engineering and Technology
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• 제13권3호
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• pp.1251-1264
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• 2018

The systematic and effective design method of a Class-D current-source resonant inverter for use in an induction cooker with zero-ripple line current is presented. The design procedure is based on the principle of the Class-D current-source resonant inverter with a simplified load network model that is a parallel equivalent circuit. An induction load characterization is obtained from a large-signal excitation test-bench based on parallel load network, which is the key to an accurate design for the induction cooker system. Accordingly, the proposed scheme provides a systematic, precise, and feasible solution than the existing design method based on series-parallel load network under low-signal excitation. Moreover, a zero-ripple condition of utility-line input current is naturally preserved without any extra circuit or control. Meanwhile, a differential-mode input electromagnetic interference (EMI) filter can be eliminated, high power quality in utility-line can be obtained, and a standard-recovery diode of bridge-rectifier can be employed. The step-by-step design procedure explained with design example. The devices stress and power loss analysis of induction cooker with a parallel load network under large-signal excitation are described. A 2,500-W laboratory prototype was developed for $220-V_{rms}/50-Hz$ utility-line to verify the theoretical analysis. An efficiency of the prototype is 96% at full load.

• Geomechanics and Engineering
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• 제18권4호
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• pp.449-457
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• 2019

Physical model tests were first performed to investigate the failure pattern of multiple pillar-roof support system. It was observed in the physical model tests, pillars were design with the same mechanical parameters in model #1, cracking occurred simultaneously in panel pillars and the roof above barrier pillars. When pillars 2 to 5 lost bearing capacity, collapse of the roof supported by those pillars occurred. Physical model #2 was design with a relatively weaker pillar (pillar 3) among six pillars. It was found that the whole pillar-roof system was divided into two independent systems by a roof crack, and two pillars collapse and roof subsidence events occurred during the loading process, the first failure event was induced by the pillars failure, and the second was caused by the roof crack. Then, for a multiple pillar-roof support system, three types of failure patterns were analysed based on the condition of pillar and roof. It can be concluded that any failure of a bearing component would cause a subsidence event. However, the barrier pillar could bear the transferred load during the stress redistribution process, mitigating the propagation of collapse or cutting the roof to insulate the collapse area. Importantly, some effective methods were suggested to decrease the risk of catastrophic collapse, and the deep-hole-blasting was employed to improve the stability of the pillar and roof support system in a room and pillar mine.

• Steel and Composite Structures
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• 제30권5호
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• pp.483-492
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• 2019

In the current study, the influence of the initial lateral (sweep) shape and the cross-sectional twist imperfection on the lateral torsional buckling (LTB) response of doubly-symmetric steel I-beams was investigated. The material imperfection (residual stress) was not considered. For this objective, standard European IPN 300 beam with different unbraced span was numerically analyzed for three imperfection cases: (i) no sweep and no twist (perfect); (ii) three different shapes of global sweep (half-sine, full-sine and full-parabola between the end supports); and (iii) the combination of three different sweeps with initial sinusoidal twist along the beam. The first comparison was done between the results of numerical analyses (FEM) and both a theoretical solution and the code lateral torsional buckling formulations (EC3 and AISC-LRFD). These results with no imperfection effects were then separately compared with three different shapes of global sweep and the presence of initial twist in these sweep shapes. Besides, the effects of the shapes of initial global sweep and the inclusion of sinusoidal twist on the critical buckling load of the beams were investigated to unveil which parameter was considerably effective on LTB response. The most compatible outcomes for the perfect beams was obtained from the AISC-LRFD formulation; however, the EC-3 formulation estimated the $P_{cr}$ load conservatively. The high difference from the EC-3 formulation was predicted to directly originate from the initial imperfection reduction factor and high safety factor in its formulation. Due to no consideration of geometric imperfection in the AISC-LFRD code solution and the theoretical formulation, the need to develop a practical imperfection reduction factor for AISC-LRFD and theoretical formulation was underlined. Initial imperfections were obtained to be more influential on the buckling load, as the unbraced length of a beam approached to the elastic limit unbraced length ($L_r$). Mode-compatible initial imperfection shapes should be taken into account in the design and analysis stages of the I-beam to properly estimate the geometric imperfection influence on the $P_{cr}$ load. Sweep and sweep-twist imperfections led to 10% and 15% decrease in the $P_{cr}$ load, respectively, thus; well-estimated sweep and twist imperfections should considered in the LTB of doubly-symmetric steel I-beams.

• 대한간호학회지
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• 제52권6호
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• pp.608-623
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• 2022

Purpose: This study aimed to evaluate the effects of a combined biofeedback and brief emotion regulation (C-BABER) program for sexually abused adolescents. Methods: This study employed a non-equivalent control group pretest-posttest design. The participants included 26 sexually abused adolescents from eight Sunflower Centers of South Korea-with 13 in the experimental group and 13 in the control group. The experimental group received four sessions of the individual C-BABER program, each lasting 60 minutes. Results: Compared with the control group, sexually abused adolescents in the experimental group exhibited significant score differences in traumatic symptoms, including depression (Z = - 2.24, p = .025), dissociation (Z = - 2.21, p = .027), anxiety (Z = - 2.02, p = .044), and posttraumatic stress (Z = - 2.01 p = .045); and impulsivity, including positive urgency (Z = - 3.35, p = .001) and negative urgency (Z = - 2.28, p = .023). Additionally, the experimental group exhibited significant score differences in meta-mood, including emotional attention (Z = - 2.45, p = .014), emotional clarity (Z = - 2.30, p = .021), and emotional repair (Z = - 2.28, p = .022); and emotional regulation modes, including emotional suppression (Z = - 2.65, p = .008) and cognitive reappraisal (Z = - 1.98, p = .047). Regarding bio-attention, significant changes were identified in the experimental group for the bio-attention rate and attention maintenance time in the posttest compared to the pretest (p = .001). Conclusion: The C-BABER program for sexually abused adolescents is effective in decreasing traumatic symptoms and impulsivity, and in improving meta-mood, emotional regulation mode, and bio-attention. Therefore, we recommend providing sexually abused adolescents the C-BABER program to help them regulate their emotions and effectively adapt to their lives.

• 지능정보연구
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• 제25권4호
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• pp.67-88
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• 2019

웹툰은 인터넷의 특징적 요소들을 활용하여 제작되는 만화 콘텐츠를 온라인 환경에서 소비 가능한 형태로 유통하는 한국형 디지털 만화 플랫폼이다. 최근 웹툰 산업의 급격한 성장과 함께 웹툰 콘텐츠의 공급량이 기하급수적으로 증가함에 따라, 효과적인 웹툰 콘텐츠 추천 방안의 필요성이 커지고 있다. 웹툰은 회화적 요소와 문학적 요소, 디지털 요소의 복합적 산물로서, 독자로 하여금 재미를 느끼게 하고 웹툰이 연출하는 상황에 이입·공감하게 하는 등 소비자의 감성을 자극하는 디지털 콘텐츠 상품이다. 따라서 웹툰이 소비자에게 전달하는 감성이 소비자가 웹툰을 선택함에 있어 중요한 기준으로 작용할 것이라 기대할 수 있다. 본 연구는 기존에 충분히 논의되지 않았던 소비자 감성을 중심으로, 웹툰 콘텐츠의 효과적인 추천을 지원할 수 있는 소비자 감성 패턴맵의 개발을 목적으로 한다. 본 연구의 수행을 위해 '네이버 웹툰' 플랫폼에서 서비스되는 200개 작품에 대한 메타데이터와 소비자 감성어휘 정보를 수집하였다. 분석 목적에 부합하지 않는 작품을 제외한 127개 작품에 대해 488개의 감성어휘가 수집되었다. 이후 수집된 감성어휘들 간 유사감성 통합, 중복감성 배제 과정을 Bottom-up 접근으로 수행하여 총 63개 감성유형으로 축소된 웹툰 특화 감성지표를 구축하였다. 구축한 감성지표에 대한 탐색적 요인분석을 수행하여 웹툰 유형을 분류할 수 있는 3개의 중요 차원을 도출하고, 이를 기준으로 K-Means 클러스터링을 수행하여 전체 웹툰을 4개 유형으로 분류하였다. 각각의 유형에 대해 웹툰-감성 2-Mode 네트워크를 구축하여 웹툰 유형별로 나타나는 감성 패턴의 특징을 살펴보았으며, 프로파일링 분석을 통해 웹툰 유형별 인사이트와 실무적으로 의미 있는 전략적 시사점을 도출할 수 있었다. 본 연구의 결과를 통해 웹툰의 추천 및 분류의 영역에서 소비자 감성의 활용 가능성을 확인하고, 웹툰 생태계 내 구성원들이 소비자를 보다 잘 이해하고 전략을 수립할 수 있도록 돕는 가이드라인을 제시하였다는 점에서 의의가 있다.

• 한국지반공학회논문집
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• 제26권6호
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• pp.57-70
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• 2010

지진에 대하여 상당히 저항력이 높다고 알려진 터널도 최근 국외에서 발생한 대 지진들에 의해서 심각한 피해를 입은 사례가 지속적으로 발생하고 있으며 터널 내진설계의 필요성을 입증하고 있다. 지진동에 대하여 터널에 발생하는 다양한 변형모드 중에서 횡방향 전단변형이 가장 치명적인 모드로 알려졌다. 본 논문에서는 횡방향 터널의 지진해석을 유사정적해석의 일종인 응답변위법으로 수행하였다. 먼저, 지반 내 변위를 계산한 결과 단일 및 이중 코사인법의 예측결과는 정확하지 않을 수 있으니 주의해야 하며 1차원 지반응답해석을 수행하는 것이 적절한 것으로 나타났다. 나아가 터널의 응답을 단순해, 해석해, 그리고 연속체 수치해석으로 계산하였다. 비교 결과, 단순해는 터널의 응답을 정확하게 예측하지 못하는 것으로 나타났다. 해석해는 균질 지반과 원형터널에서는 적절하나 비균질 지반에서는 적절하지 않은 것으로 나타났다. 수치해석은 모든 경우에 적용 가능한 가장 정확한 방법인 것으로 나타났다. 또한, 선형해석은 보수적이며 지반의 비선형성을 고려하는 것이 적절한 것으로 나타났다.