• 한국자동차공학회논문집
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• 제19권6호
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• pp.61-67
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• 2011

The cooling module needs enough space (or distance) from hood to absorb the energy from any pedestrian collision. Downsized cooling module for pedestrian protection is important to reduce the severity of pedestrian injury. When a vehicle collision happens, the downsized cooling module is required to reduce the risk of injury to the upper legs of adults and the heads of children. In this study, the performance of cooling module to cool the engine was investigated under 25% height reduction. The heat dissipation and pressure drop characteristics have been experimentally studied with the variation of coolant flow rate, air inlet velocity and A/C operation ON/OFF for the downsized cooling module. The results indicated that the cooling performance was about 94% level compared to that of the conventional cooling module. Therefore, we checked that the cooling module had good performance, and expected that the cooling module could meet the same cooling performance as conventional cooling module through optimization of components efficiency.

• 정보처리학회논문지A
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• 제13A권2호
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• pp.171-176
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• 2006

이 논문에서 우리는 FPGA에서의 고속 푸리에 변환(FFT)을 함에 있어 에너지를 효율적으로 사용하는 디자인을 제안하고자 한다. FPGA에서의 FFT 구조들은 에너지 손실을 최소화 하기 위해서 설계되어왔다. 가로와 세로의 병렬성 정도와 같은 구조적인 성능 지표들을 정의 했으며, 설계 영역은 설계 디자인들의 조합을 통해서 생성했다. 우리는 에너지를 효율적으로 사용하는 디자인들을 얻기 위해 상위 계층 동작 예측을 사용하여 디자인의 고려사항들을 결정하였다. 우리는 다앙한 예측을 위해서 한 무리의 병렬성, radix, 저장 형태의 선택등을 갖는 성능 지표화된 디자인의 집합을 Xilinx Virtex-2 상에서 구현하였다. 우리의 디자인들은 Xilinx 라이브러리에 있는 최적화된 디자인들보다 에너지 손실이 57%에서 78%정도 감소했다. 에너지-영역-시간(EAT)과 같은 이해하기 쉬운 지표를 이용한 결과, 우리의 디자인들이 Xilinx의 디자인보다 3-13 배의 성능 개선 효과를 나타냈다.

• Steel and Composite Structures
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• 제37권3호
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• pp.259-272
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• 2020

In this study a new hysteretic damper for seismic retrofit of soft-first story structures is proposed and its seismic retrofit effect is evaluated. The damper consists of one steel column member and two flexural fuses at both ends made of steel plates with reduced section, which can be placed right beside existing columns in order to minimize interference with passengers and automobiles in the installed bays. The relative displacement between the stories forms flexural plastic hinges at the fuses and dissipate seismic energy. The theoretical formulation and the design procedure based on plastic analysis is provided for the proposed damper, and the results are compared with a detailed finite-element (FE) model. In order to apply the damper in structural analysis, a macromodel of the damper is also developed and calibrated by the derived theoretical formulas. The results are compared with the detailed FE analysis, and the efficiency of the damper is further validated by the seismic retrofit of a case study structure and assessing its seismic performance before and after the retrofit. The results show that the proposed hysteretic damper can be used effectively in reducing damage to soft-first story structures.

• Advances in concrete construction
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• 제1권3호
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• pp.253-272
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• 2013

The use of steel bracing systems is a popular method for the strengthening of existing reinforced concrete (RC) frames and may lead to a substantial increase of both strength and stiffness. However, in most retrofitting cases, the main target is the increase of the energy dissipation capacity. This paper studies numerically the efficiency of a specific strengthening methodology which utilizes a steel link element having a cross-section of various shapes, connected to the RC frame through bracing elements. The energy is dissipated through the yielding of the steel link element. The case studied is a typical one bay, single-storey RC frame, constructed according to older code provisions, which is strengthened through two different types of link elements. The presented numerical models are based on tests which are simulated in order to gain a better insight of the behaviour of the strengthened structures, but also in order to study the effects of different configurations for the link element. The behaviour of the strengthened frames is studied with respect to the one of the original bare frame. Moreover, the numerically obtained results are compared to the experimentally obtained ones, in order to verify the effectiveness of the applied simulation methodology.

• Earthquakes and Structures
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• 제19권6호
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• pp.459-469
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• 2020

An external prestressed steel-bar truss unit was developed as a new strengthening technology to enhance the seismic performance of an in-plane masonry wall structure while taking advantage of the benefits of a prestressed system. The presented method consists of six steel bars: two prestressed vertical bars to introduce a prestressing force on the masonry wall, two diagonal bars to resist shear deformation, and two horizontal bars to maintain the configuration. To evaluate the effects of this new technique, four full-scale specimens, including a control specimen, were tested under combined loadings that included constant-gravity axial loads and cyclic lateral loads. The experimental results were analyzed in terms of the shear strength, initial stiffness, dissipated energy, and strain history. The efficiency of the external prestressed steel-bar truss unit was validated. In particular, a retrofitted specimen with an axial load level of 0.024 exhibited a more stable post behavior and higher energy dissipation than a control specimen with an observed complete sliding failure. The four vertical bars of the adjacent retrofitting units created a virtual column, and their strain values did not change until they reached the peak shear strength. The shear capacity of the masonry wall structure with external prestressed steel-bar truss units could be predicted using the model suggested by Yang et al.

• Nuclear Engineering and Technology
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• 제55권11호
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• pp.4120-4124
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• 2023

High-level radioactive waste produced by nuclear power plants are disposed subterraneously utilizing an engineered barrier system (EBS). A gap inevitably exists between the disposal canisters and buffer materials, which may have a negative effect on the thermal transfer and water-blocking efficiency of the system. As few previous experimental works have quantified this effect, this study aimed to create an experimental model for investigating differences in the temperature changes of bentonite buffer in the presence and absence of air gaps between it and a surrounding stainless steel cell. Three test scenarios comprised an empty cell and cells partially or completely filled with bentonite. The temperature was measured inside the buffers and on the inner surface of their surrounding cells, which were artificially heated. The time required for the entire system to reach 100℃ was approximately 40% faster with no gap between the inner cell surface and the bentonite. This suggests that rock-buffer spaces should be filled in practice to ensure the rapid dissipation of heat from the buffer materials to their surroundings. However, it can be advantageous to retain buffer-canister gaps to lower the peak buffer temperature.

• Structural Engineering and Mechanics
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• 제91권1호
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• pp.75-86
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• 2024

In this paper, the porous metal PM-35 is proposed as the filler material of filled thin-walled tubes (FTTs), and a series of experimental study is conducted to investigate the dynamic behavior and energy absorption performance of PM-35 filled thin-walled tubes under impact loading. Firstly, cylinder solid specimens of PM-35 steel are tested to investigate the impact mechanical behavior by using the Split Hopkinson pressure bar set (SHP); Secondly, the filled thin-walled tube specimens with different geometric parameters are designed and tested to investigate the feasibility of PM-35 steel applied in FTTs by the orthogonal test. According to the results of this research, it is concluded that PM-35 steel is with the excellent characteristics of high energy absorption capacity and low yield strength, which make it a potential filler material for FTTs. The micron-sizes pore structure of PM-35 is the main reason for the macroscopic mechanical behavior of PM-35 steel under impact loading, which makes the material to exhibit greater deformation when subjected to external forces and obviously improve the toughness of the material. In addition, PM-35 steel core-filled thin-wall tube has excellent energy absorption ability under high-speed impact, which shows great application potential in the anti-collision structure facilities of high-speed railway and maglev train. The parameter V0 is most sensitive to the energy absorption of FTT specimens under impact loading, and the sensitivity order of different variations to the energy absorption is loading speed V0>D/t>D/L. The loading efficiency of the FTT is affected by its different geometry, which is mainly determined by the sleeve material and the filling material, which are not sensitive to changes in loading speed V0, D/t and D/L parameters.

• 마이크로전자및패키징학회지
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• 제21권4호
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• pp.1-13
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• 2014

The paper gives an overview of the concepts, basic requirements, and trends regarding packaging technologies of power modules in hybrid (HEV) and electric vehicles (EV). Power electronics is gaining more and more importance in the automotive sector due to the slow but steady progress of introducing partially or even fully electric powered vehicles. The demands for power electronic devices and systems are manifold, and concerns besides aspects such as energy efficiency, cooling and costs especially robustness and lifetime issues. Higher operation temperatures and the current density increase of new IGBT (Insulated Gate Bipolar Transistor) generations make it more and more complicated to meet the quality requirements for power electronic modules. Especially the increasing heat dissipation inside the silicon (Si) leads to maximum operation temperatures of nearly $200^{\circ}C$. As a result new packaging technologies are needed to face the demands of power modules in the future. Wide-band gap (WBG) semiconductors such as silicon carbide (SiC) or gallium nitride (GaN) have the potential to considerably enhance the energy efficiency and to reduce the weight of power electronic systems in EVs due to their improved electrical and thermal properties in comparison to Si based solutions. In this paper, we will introduce various package materials, advanced packaging technologies, heat dissipation and thermal management of advanced power modules with extended reliability for EV applications. In addition, SiC and GaN based WBG power modules will be introduced.

• Elastomers and Composites
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• 제47권1호
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• pp.54-64
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• 2012

본 연구에서는 polar 한 silica 와 non-polar 한 고무사이의 친화력을 증대시키기 위하여 SBR 분자 주쇄에 acrylonitrile 을 도입시킨 acrylonitirle functionalized emulsion SBR 의 물성에 관하여 연구하였다. Acrylonitrile의 nitrile group 은 silica 표면의 silanol group 과 H-bond 를 형성할 수 있음으로 polar 한 silica 표면에 흡착되는 가교촉진제를 줄이고 가황반응을 촉진시키는 것으로 판단된다. SBR 및 AN-SBR 에 PEG 를 적용한 컴파운드의 경우 PEG 와 silica 표면의 silanol group 과의 상용성이 높아 가교촉진제가 polar 한 silica 표면에 흡착됨을 줄여 가교시간이 단축된 것으로 판단된다. 기계적 물성에서 AN-SBR 컴파운드는 SBR 1721 컴파운드 대비 100%, 300%에서 높은 모듈러스 값을 나타내었다. 이러한 결과는 AN-SBR 의 높은 분자량 및 nitrile group 의 도입에 따른 가교도의 상승에 의한 결과로 판단된다. 동적점탄특성 결과에서 AN-SBR 컴파운드는 SBR 1721 컴파운드 대비 $60^{\circ}C$ 에서 낮은 tan ${\delta}$ 값을 나타내었으며, 이는 nitrile group 과 silica 사이의 친화력에 따른 filler-rubber interaction의 향상에 의해 반복변형에 의한 energy dissipation 이 낮은 것으로 판단된다.

• 에너지공학
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• 제28권4호
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• pp.35-41
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• 2019

기존에 차량용 안개등으로 사용되었던 할로겐 광원은 전력소모가 증가하고 수명이 짧기 때문에 이러한 단점을 극복하기 위해 자동차 광원은 LED로 점차 바뀌고 있다. 그러나 차량용 LED 안개등을 점등하였을 경우에는 LED에서 발생하는 고열로 인해 안개등 수명을 단축시키는 단점이 있다. 안개등 내부에서 LED에 의해 발생된 열은 주로 히트싱크에 의해 배출되지만, 나머지 열은 거의 대부분 대류를 통해 외부로 배출된다. 이러한 대류에 의한 냉각효율이 저하되면 열에너지는 램프의 주요부품인 렌즈, 리플렉터, 베젤 등에 열을 발생시키거나 LED 광원에 고온을 발생시켜 LED 안개등의 수명을 단축시킨다. 따라서, 본 연구에서는 히트싱크에 의한 방열방식 이외에도 냉각효율에 중요한 영향이 미치는 대류에 의한 방열성능을 개선하고자 하였다. 이를 위해 차량용 LED 안개등 내부공기를 외부로 흡·배출시킬수 있는 통풍구 설치 위치를 결정하기 위한 열유동해석을 수행하여 최적의 설계가 되도록 하였다. 공기의 평균속도는 기존 프로토타입인 Case1에 비해 Case3, Case2의 순으로 증가되었고 Case3의 증가폭이 다른 Case에 비해 상대적으로 큰 것을 알 수 있었다. 이는 안개등 상·하에 설치된 통풍구가 온도차이에 따라 생성되는 대류현상을 적절하게 유도하기 때문에 공기의 속도 증가와 함께 열을 효율적으로 배출시켰기 때문인 것으로 판단하였다.