• Tribology and Lubricants
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• 제30권1호
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• pp.46-51
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• 2014

In this study, we attempted to characterize the physical meaning of the design parameters used for automobile passive dampers by considering the slit, disc, and hole, which influence the pressure characteristics. We also analyzed the change in the pressure characteristics when mixing various slits and discs. Finally, we used a computer simulation to implement lag according to nitrogen gas and analyzed the dependence of frequency on the nitrogen gas pressure.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.813-816
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• 2005

This paper presents a method for harmonic elimination and reactive power compensation using an intervening firing method and passive power filter with is suitable to compensate rapidly changing loads and reactive power. The proliferation of three-phase thyristor phase-controlled converter of DC motor drives into a power system has the potential to increase the harmonic levels in the power system. The design procedure of an intervening firing method and passive power filter capable of reducing the voltage and current harmonics produced by converter supplied from a source having internal large inductive impedance is offered. The analysis uses the or CAD PSpice to model three-phase thyristor phase-controlled converter of DC motor drives as well as the system.

• KIEAE Journal
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• 제11권4호
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• pp.63-70
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• 2011

In respond to the global energy crisis and climate change, there have been many ongoing national efforts to develop a sustainable housing prototype followed by "2 million Green Home Project" in Korea. More than 50% of nation's population are currently living in apartment housing thus the country is seriously in need of developing green apartment prototype. In this research, we focused on energy-conservative green apartment design prototype that have both passive components and active systems explored in a systemic design approach. After selecting an existing basic apartment unit, we analyzed and compared statistical data with the simulated annual energy consumption to match these two data sets for validating simulation accuracy performed with TRNSYS package. We performed energy simulations with different passive design factors such as varied insulation thickness, window types and infiltration rates as well as the active design factors including boilers and lighting fixtures to analyze their impacts on the energy performance of the housing unit using TRNSYS software. As a result, we acquired significant energy reduction effect with explored design strategies but the life cycle cost analysis for the final design guidline would need to be performed. In this study, we focused on a systematic comparative energy analysis based on TRNSYS that can improve the design of a green apartment housing.

• 한국공간구조학회논문집
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• 제17권4호
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• pp.123-132
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• 2017

A smart tuned mass damper (TMD) was developed to provide better control performance than a passive TMD for reduction of earthquake induced-responses. Because a passive TMD was developed decades ago, optimal design methods for structural parameters of a TMD, such as damping constant and stiffness, have been developed already. However, studies of optimal design method for structural parameters of a smart TMD were little performed to date. Therefore, parameter studies of structural properties of a smart TMD were conducted in this paper to develop optimal design method of a smart TMD under seismic excitation. A retractable-roof spatial structure was used as an example structure. Because dynamic characteristics of a retractable-roof spatial structure is changed based on opened or closed roof condition, control performance of smart TMD under off-tuning was investigated. Because mass ratio of TMD and smart TMD mainly affect control performance, variation of control performance due to mass ratio was investigated. Parameter studies of structural properties of a smart TMD was performed to find optimal damping constant and stiffness and it was compared with the results of optimal passive TMD design method. The design process developed in this study is expected to be used for preliminary design of a smart TMD for a retractable-roof spatial structure.

• Nuclear Engineering and Technology
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• 제55권12호
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• pp.4335-4349
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• 2023

Nuclear marine propulsion has been emerging as a next generation carbon-free power source, for which proper passive residual heat removal systems (PRHRSs) are needed for long-term safety. In particular, the characteristics of unlimited operation time and compact design are crucial in maritime applications due to the difficulties of safety aids and limited space. Accordingly, a compact and long-term-operable PRHRS has been proposed with the key design concept of using both air cooling and seawater cooling in tandem. To confirm its feasibility, this study conducted system design and a transient analysis in an accident scenario. Design results indicate that seawater cooling can considerably reduce the overall system size, and thus the compact and long-term-operable PRHRS can be realized. Regarding the transient analysis, the Multi-dimensional Analysis of Reactor Safety (MARS-KS) code was used to analyze the system behavior under a station blackout condition. Results show that the proposed design can satisfy the design requirements with a sufficient margin: the coolant temperature reached the safe shutdown condition within 36 h, and the maximum cooling rate did not exceed 40 ℃/h. Lastly, it was assessed that both air cooling and seawater cooling are necessary for achieving long-term operation and compact design.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 춘계학술대회 논문집
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• pp.327-328
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• 2007

• Steel and Composite Structures
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• 제28권6호
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• pp.691-708
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• 2018

An innovative Hybrid Passive Resistive configuration for Truss Girder Frames (HPR-TGFs) is introduced in the present study. The proposed system is principally consisting of Fluid Viscous Dampers (FVDs) and Buckling Restrained Braces (BRBs) as its seismic resistive components. Concurrent utilization of these devices will develop an efficient energy dissipating mechanism which is able to mitigate lateral displacements as well as the base shear, simultaneously. However, under certain circumstances which the presence of FVDs might not be essential, the proposed configuration has the potential to incorporate double BRBs in order to achieve the redundancy of alternative load bearing paths. This study is extending the modern Direct Displacement Based Design (DDBD) procedure as the design methodology for HPR-TGF systems. Based on a series of nonlinear time history analysis, it is demonstrated that the design outcomes are almost identical to the pre-assumed design criteria. This implies that the ultimate characteristics of HPR-TGFs such as lateral stiffness and inter-story drifts are well-proportioned through the proposed design procedure.

• Nuclear Engineering and Technology
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• 제53권2호
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• pp.498-508
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• 2021

Micro reactors are increasingly being considered for utilization as distributed power sources. Hence, the probabilistic safety assessment (PSA) of a direct supercritical-CO₂-cooled fast reactor, called micro modular reactor (MMR), was performed in this study; this reactor was developed using innovative design concepts. It adopted a modular design and passive safety systems to minimize site constraints. As the MMR is in its conceptual design phase, design weaknesses and valuable safety insights could be identified during PSA. Level 1 internal event PSA was carried out involving literature survey, system characterization, identification of initiating events, transient analyses, development of event trees and fault trees, and quantification. The initiating events and scenarios significantly contributing to core damage frequency (CDF) were determined to identify design weaknesses in MMR. The most significant initiating event category contributing to CDF was the transients with the power conversion system initially available category, owing to its relatively high occurrence frequency. Further, an importance analysis revealed that the safety of MMR can be significantly improved by improving the reliability of reactor trip and passive decay heat removal system operation. The findings presented in this paper are expected to contribute toward future applications of PSA for assessing unconventional nuclear reactors in their conceptual design phases.

• 전자공학회논문지
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• 제54권1호
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• pp.26-32
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• 2017

본 논문에서는 설계 요구가 높고, 전력 소모가 높은 opamp를 이용하는 기존의 능동형 적분기를, 수동형 적분기로 대체하여 고속의 저전력, 고해상도 특성을 갖는 incremental delta-sigma ADC를 소개한다. 능동형 적분기에서 수동형 적분기로의 변환을 위해, 기존의 능동형 적분기의 특성을 분석하였다. 이를 바탕으로 opamp의 설계 요구를 낮추고, 더 나아가 opamp를 사용하지 않는 저전력의 수동형 적분기를 제안하였다. 65nm 공정을 이용하여 수동형 적분기로 구성된 1차 single-bit incremental delta-sigma ADC를 설계하였다. Transistor-level 시뮬레이션 결과, 이는 supply 전압이 1.2V인 상황에서 modulator만 0.6uW, digital filter를 포함한 ADC 전체에서 6.25uW를 소모하며 BW 22KHz, SNDR 71dB, dynamic range 74.6dB을 달성하였다.

• Geomechanics and Engineering
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• 제7권3호
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• pp.263-277
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• 2014

In the conventional design of retaining structures in a seismic zone, seismic inertia forces are commonly assumed to act upwards and towards the wall facing to cause a maximum active thrust or act upwards and towards the backfill to cause a minimum passive resistance. However, under certain circumstances this design approach might underestimate the dynamic active thrust or overestimate the dynamic passive resistance acting on a rigid retaining structure. In this study, a new analytical method for dynamic active and passive forces in c-${\phi}$ soils with an infinite slope was proposed based on the Rankine earth pressure theory and the Mohr-Coulomb yield criterion, to investigate the influence of seismic inertia force directions on the total active and passive forces. Four combinations of seismic acceleration with both vertical (upwards or downwards) and horizontal (towards the wall or backfill) directions, were considered. A series of dimensionless dynamic active and passive force charts were developed to evaluate the key influence factors, such as backfill inclination ${\beta}$, dimensionless cohesion $c/{\gamma}H$, friction angle ${\phi}$, horizontal and vertical seismic coefficients, $k _h$ and $k_v$. A comparative study shows that a combination of downward and towards-the-wall seismic inertia forces causes a maximum active thrust while a combination of upward and towards-the-wall seismic inertia forces causes a minimum passive resistance. This finding is recommended for use in the design of retaining structures in a seismic zone.