• 한국산학기술학회논문지
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• 제13권5호
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• pp.2015-2022
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• 2012

본 논문은 항공전자장비의 구조해석을 통한 하우징과 인쇄회로기판의 해석과 설계에 관한 것으로 대기자료 컴퓨터 개발 사례를 통한 연구결과이다. 항공기에 장착되는 전자장비는 전기적인 특성 외에도 운용환경에 따른 구조 설계가 매우 중요하고 설계 단계에서부터 해석을 통한 입증이 되어야 한다. 본 연구에서는 장착되는 항공 장비의 응력과 진동 요구도를 분석하여 해석 결과를 통하여 설계에 적용하고 요구도에 대해서 입증하는 방법에 대한 것이다. 구조 해석은 상용 소프트웨어를 사용하였으며 하우징의 내부 리브 설계에 대한 적합성을 확인하고 인쇄회로 기판의 변위를 계산하여 전자 부품 배치에 활용하는 방법에 대해서 제시하였다.

• Structural Engineering and Mechanics
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• 제11권2호
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• pp.199-210
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• 2001

Axially compressed circular cylinders repeat symmetry-breaking bifurcation in the postbuckling region. There exist stable equilibria with all symmetry broken in the buckled configuration, and the minimum postbuckling strength is attained at the deep bottom of closely spaced equilibrium branches. The load level corresponding to such postbuckling stable solutions is usually much lower than the initial buckling load and may serve as a strength limit in shell stability design. The primary concern in the present paper is to compute these possible postbuckling stable solutions at the deep bottom of the postbuckling region. Two computational approaches are used for this purpose. One is the application of individual procedures in computational bifurcation theory. Path-tracing, pinpointing bifurcation points and (local) branch-switching are all applied to follow carefully the postbuckling branches with the decreasing load in order to attain the target at the bottom of the postbuckling region. The buckled shell configuration loses its symmetry stepwise after each (local) branch-switching procedure. The other is to introduce the idea of path jumping (namely, generalized global branch-switching) with static imperfection. The static response of the cylinder under two-parameter loading is computed to enable a direct access to postbuckling equilibria from the prebuckling state. In the numerical example of an elastic perfect circular cylinder, stable postbuckling solutions are computed in these two approaches. It is demonstrated that a direct path jump from the undeformed state to postbuckling stable equilibria is possible for an appropriate choice of static perturbations.

• ETRI Journal
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• 제38권4호
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• pp.654-664
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• 2016

This paper presents a transformer-based reconfigurable synchronous boost converter. The lowest maximum power point tracking (MPPT)-input voltage and peak efficiency of the proposed boost converter, 20 mV and 88%, respectively, were achieved using a reconfigurable synchronous structure, static power loss minimization design, and efficiency boost mode change (EBMC) method. The proposed reconfigurable synchronous structure for high efficiency enables both a transformer-based self-startup mode (TSM) and an inductor-based MPPT mode (IMM) with a power PMOS switch instead of a diode. In addition, a static power loss minimization design, which was developed to reduce the leakage current of the native switch and quiescent current of the control blocks, enables a low input operation voltage. Furthermore, the proposed EBMC method is able to change the TSM into IMM with no additional time or energy loss. A prototype chip was implemented using a $0.18-{\mu}m$ CMOS process, and operates within an input voltage range of 9 mV to 1 V, and an output voltage range of 1 V to 3.3 V, and provides a maximum output power of 37 mW.

• Structural Engineering and Mechanics
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• 제73권6호
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• pp.667-684
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• 2020

In this article, the static responses of layered magneto-electro-thermo-elastic (METE) plates in thermal environment have been investigated through FE methods. By using Reddy's third order shear deformation theory (TSDT) in association with the Hamilton's principle, the direct and derived quantities of the coupled system have been obtained. The coupled governing equations of METE plates have been derived through condensation technique. Three layered METE plates composed of piezoelectric and piezomagnetic phases are considered for evaluation. For investigating the correctness and accuracy, the results in this article are validated with previous researches. In addition, a special attention has been paid to evaluate the influence of different electro-magnetic boundary conditions and pyrocoupling on the coupled response of METE plates. Finally, the influence of stacking sequences, magnitude of temperature load and aspect ratio on the coupled static response of METE plates are investigated in detail.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 제35회 춘계학술대회
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• pp.137-142
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• 2002

The fluid mechanics and operating conditions of gas-lubricated proceeding bearings in micro rotating machinery such as micro polarization modulator and micro gas turbine are different from their larger size ones. Due to non-continuum effects, there is a slip of gas at the walls. Thus in this paper, the slip flow effect is considered to estimate the pressure distribution and load-carrying capacity of micro gas-lubricated proceeding bearings as the local Knudsen number at the minimum film thickness is greater than 0.01. Based on the compressible Reynolds equation with slip flow, the static characteristics of micro gas-lubricated proceeding bearings are obtained. Numerical predictions compare the pressure distribution and load capacity considering slip flow with the performance of micro proceeding bearings without slip f]ow for a range of bearing numbers and eccentricities. The results clearly show that the slip flow effect on the static characteristics is considerable and becomes more significant as temperature increases.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.941-946
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• 2002

Short reinforced concrete bridge piers are particularly susceptible to shear failure as a consequence of the high shear/moment ratio and conservatism in the flexural strength design of existing RC bridge pier, which were constructed before 1992. In addition, shear failure is brittle and involves rapid strength degradation. Inelastic shear deformation is thus unsuitable for ductile seismic response. It is, however, believed that there are not many experimental research works for shear failure of the existing RC bridge pier in Korean peninsula subjected to earthquake motions. The object of this research is to evaluate the seismic performance of existing circular RC bridge piers by the quasi-static test. Existing RC bridge piers were moderate seismically designed in accordance with the conventional provisions of Korea Highway Design Specification. This study has been performed to verify the effect of aspect ratio (column height-diameter ratio). Quasi-static test has been done to investigate the physical seismic performance of RC bridge piers, such as lateral force-displacement hysteric curve, envelope curve etc.

• 한국안전학회지
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• 제30권3호
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• pp.107-113
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• 2015

The goal of this paper is to investigate structural integrity factors of RMI(reflective metal insulation) to confirm the design requirements in nuclear power plant. Currently, a glass wool insulation is using now, but it will gradually be replaced with the reflective metal insulation maded by stainless steel plates. The main function of an insulation is to minimize a heat loss of vessel and pipes in RCS(reactor coolant system). It has to maintain structural a integrity in nuclear power plant life duration. In this study, the structural integrity analysis was carried out both multi-plate and outer shell plate by using a static analysis and experimental test. First, inner multi-plate has a self support structure for being air space. Because the effect of total static weight in multi-layer plate is low, a plate collapse possibility is not high. Considering optimum thin plate pressing process, it has to pre-check the basic physical properties. Second, the outer segment thickness and stiffener shape are verified by the numerical static analysis, and sample test for both type of panel and cylindrical pipe model.

• 한국정밀공학회지
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• 제29권10호
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• pp.1062-1069
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• 2012

This paper suggests a computational modeling to reflect static/dynamic characteristics of LM bearings. A theoretical study for modeling LM bearings is elucidated by using the Hertz contact theory, the Lagrange's equation of motion, normal mode analysis and a calculation of equivalent moment center. The complex geometry of LM bearings is replaced by a simplified model with eight springs only. The suggested model reflects static and dynamic characteristics of LM bearings without any consideration for the shape of the bed or stages on the LM bearings. The modal experimental results are compared to the simulation results with the suggested computational modeling. The difference between the experiments and simulation is calculated less than 8%.

• Earthquakes and Structures
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• 제10권4호
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• pp.849-865
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• 2016

Beside the invaluable advancements in constructing more secure buildings, the post-earthquake inspections have reported considerable damages. In other words, the modern buildings satisfactorily decrease fatalities but the monetary impacts still mostly remain an unsolved concern of the stakeholders, the insurance companies and society together. Therefore, the fundamental target of the researches shifted from current force-based seismic design regulations to the Performance-Based earthquake engineering (PBEE). At the moment, some probabilistic approaches, such as PEER framework have been developed to predict the performance of building at any desired hazard levels. These procedures are so time-consuming, to which many details are needed to be assigned. It causes their usage to be limited. On that account, developing more straightforward methods seems indispensable. The main objective of the present paper is to adapt an equivalent static method in different damage states. Consequently, constant damage spectrums corresponding to different limit states, soil types, ductility and fundamental periods are plotted and tri-linear formulas are proposed for further applications. Moreover, the sensitivity of outcomes to the employed hysteresis model, ductility, viscous damping and site soil type is investigated. Finally, a case study building with moment-resisting R.C. frame is evaluated based on the both of new and current methods to ensure applicability of the proposed method.

• 한국멀티미디어학회논문지
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• 제18권6호
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• pp.763-771
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• 2015

The kinetic typography animates the static text and it will enable the delivery the opinion and emotion, but we should use professional software or do complex coding precess to create a motion into an existing static text. In this paper, we propose the primitive motion API which is the way to configure the kinetic typography easily by adding a motion into the static text. In the pursuit of this purpose, we analyzed the movement of the text, defined the underlying levels of the movement and designed the primitive motion API to express the kinetic typography promptly. Furthermore, we verified the performance of the primitive motion API by testing the usability. Using the primitive motion API to implement the kinetic typography explicitly might substitute for tedious coding process and usage of the existing professional software so it makes anyone be able to apply the kinetic typography in a variety of applications.