• Structural Engineering and Mechanics
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• 제82권6호
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• pp.735-745
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• 2022

The suspension thyristor valve can generate tremendous vertical acceleration responses in layers and large tension forces in hangers. A shaking table test of a scaled-down model of thyristor valves suspended on a hall building is performed to qualify the risk of vertical uplift of two representative types of valves, the chain valve and the rigid valve. Besides, an analytical model is established to investigate the source of the slackening of hangers. The test results show that the valves frequently experience a large vertical acceleration response. The soft spring joint can significantly reduce acceleration, but is still unable to prevent vertical uplift of the chain valve. The analytical model shows a stiffer roof and inter-story connection both contribute to a higher risk of vertical uplift for a rigid valve. In addition, the planar eccentricity and short hangers, which result in torsional motion of the valve, increase the possibility of vertical uplift for a chain valve. Therefore, spring joints with additional viscous dampers and symmetric layout in each layer are recommended for the rigid and chain valve, respectively, to prevent the uplift of valves.

• 한국전자통신학회논문지
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• 제15권6호
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• pp.1055-1060
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• 2020

본 연구는 축소형 항공기의 레이다 단면적 분석 및 측정에 대한 연구이다. 사전에 축소형 항공기에 대한 레이다 단면적 특성을 전자기 해석 툴을 사용하여 분석하고 실제 축소형 항공기를 제작하여 무반사실에서 측정하였다. 측정 시 구모델을 사용하여 RCS 특성의 기준 데이터로 적용하여 실제 축소형 모델의 시험 결과 데이터에 적용하였다. 측정 방법은 시간 게이팅을 적용하여 무반사실 내부에서 산란되는 성분에 대한 영향을 제거하여 측정의 정확성을 향상시켰다. 축소형 모델의 RCS 시험 결과는 사전 해석 결과와 같이 초단파 대역에서 상대적으로 RCS 특성이 높게 측정되었다. 향후 본 연구를 통하여 파장이 상대적으로 큰 VHF/UHF 대역 레이다의 표적에 대한 RCS 분석 및 측정에 대한 특성 기술에 활용할 예정이다.

• Journal of Mechanical Science and Technology
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• 제20권1호
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• pp.59-65
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• 2006

A half-scaled large test model for the main components of the real annular structure was built and the thermal behaviors were experimented and obtained by thermal cyclic loads. The model design and the test conditions for the thermal loads were determined to take into consideration the thermal and mechanical loads acting on the real annular structure by finite element analyses. Temperature profiles and strains of the main components of the model were measured at an early stage of the test and periodically throughout the test in the given test conditions. After completion of the thermal cyclic tests, no evidence of crack initiation and propagation were identified by a dye penetration test. The measured strains at the critical parts were slightly increased proportionally with the increase in the number of the thermal cycles.

• Earthquakes and Structures
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• 제19권2호
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• pp.103-117
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• 2020

The effect of the foundation size on the efficiency of seismic base isolation using a layer of stone pebbles is experimentally investigated. Four scaled models of buildings with different stiffnesses (from very stiff to soft) were tested, each with the so-called small and large foundation, and exposed to four different accelerograms (different predominant periods and durations). Tests were conducted so that the strains in the model remained elastic and afterwards the models were tested until collapse. Each model was tested for the case of the foundation being supported on a rigid base and on an aseismic layer. Compared to the smaller foundation, the larger foundation results in a reduced rocking effect, higher earthquake forces and lower bearing capacity of the tested models, with respectable efficiency (reduced strain/stress, displacement and increase of the ultimate bearing capacity of the model) for the considered seismic base isolation compared to the foundation on a rigid base.

• 제어로봇시스템학회논문지
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• 제5권5호
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• pp.622-629
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• 1999

This paper discusses a real time multi-tasking system model and a development environment for an elevator control system. Recently, as the elevator systems become large-scaled and operate with high speed, there are lots of software tasks to be processed with time constraints. Thus, the control systems are designed with distributed control structure and characteristics of typical real time systems. For stuructural design of such real time system, we introduce a multi-tasking model based on a real time operating system model and an software development environment based on virtual protopyping which simulates real system operation in the cross development of a new elevator system with distributed control structure and its system reliability can be verified through numerous field tests.

• 한국전자파학회논문지
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• 제14권7호
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• pp.705-711
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• 2003

본 연구에서는 고출력 소자로서 각광받고 있는 AlGaN/GaN HEMT 2$\times$100 $\mu\textrm{m}$ 소자(사파이어 기판)에 대해 열 효과가 포함된 대신호 모델링을 수행하였다. 완성된 대신호 모델을 이용하여 9 mm, 15 mm 사이즈 소자로의 스케일링을 통해 전력증폭기를 설계하였으며 제작된 결과와 비교, 해석하였다. 대신호 모델링은 수렴성과 해석 속도면에서 탁월한 장점을 갖는 수식 기반의 경험적 방법을 사용하였다. Pulsed I-V 측정을 통하여 열모델의 가장 중요한 파라미터인 열 시상수 및 열 저항을 추출하였으며 이를 통하여 완벽한 열 모델 제작이 가능하였다. 제작된 전력증폭기 모듈의 측정결과와 비교를 통하여 본 연구에서 제안된 열 모델이 매우 정확함을 확인할 수 있으며 전력증폭기와 같이 큰 사이즈의 소자를 사용해야 하는 회로의 경우에는 열 효과가 포함된 모델을 사용하여 더욱 정확한 모델링 결과를 얻을 수 있음을 확인할 수 있다.

• Nuclear Engineering and Technology
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• 제53권9호
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• pp.3068-3084
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• 2021

Investigations of large commercial aircraft impact effect on nuclear power plant (NPP) buildings have been drawing extensive attentions, particularly after the 9/11 event, and this paper aims to experimentally assess the damage and vibrations of NPP buildings subjected to aircraft crash. In present Part I, two shots of reduce-scaled model test of aircraft impacting on NPP building were carried out. Firstly, the 1:15 aircraft model (weighs 135 kg) and RC NPP model (weighs about 70 t) are designed and prepared. Then, based on the large rocket sled loading test platform, the aircraft models were accelerated to impact perpendicularly on the two sides of NPP model, i.e., containment and auxiliary buildings, with a velocity of about 170 m/s. The strain-time histories of rebars within the impact area and acceleration-time histories of each floor of NPP model are derived from the pre-arranged twenty-one strain gauges and twenty tri-axial accelerometers, and the whole impact processes were recorded by three high-speed cameras. The local penetration and perforation failure modes occurred respectively in the collision scenarios of containment and auxiliary buildings, and some suggestions for the NPP design are given. The maximum acceleration in the 1:15 scaled tests is 1785.73 g, and thus the corresponding maximum resultant acceleration in a prototype impact might be about 119 g, which poses a potential threat to the nuclear equipment. Furthermore, it was found that the nonlinear decrease of vibrations along the height was well reflected by the variations of both the maximum resultant vibrations and Cumulative Absolute Velocity (CAV). The present experimental work on the damage and dynamic responses of NPP structure under aircraft impact is firstly presented, which could provide a benchmark basis for further safety assessments of prototype NPP structure as well as inner systems and components against aircraft crash.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2002년도 춘계 학술발표회 논문집
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• pp.203-210
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• 2002

The past bridge design specifications of Korea didn't include 1imitation on the amount of lap splices in the plastic hinge zone of piers, and so do current specifications. But these specifications include just limitation on the minimal length of lap splices. Thus, a large majority of non-seismically designed bridge piers may have lap splices in plastic hinge zone. In this study, model pier was selected among existent bridge piers whose failure mode is complex shear-flexure mode. Full scaled RC pier models whose aspect ratio is about 2.67 were constructed and quasi static test according to the drift level history was implemented. From the test results, effect of the lap splices on the seismic performance of bridges piers was analyzed, and the seismic capacity of the model bridges was evaluated by capacity spectrum method.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2005년도 추계종합학술대회
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• pp.643-646
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• 2005

This paper presents CARMA (Cycle-Accurate Retargetable Micro-Architecture) as efficient framework for SoC-centric pipelined instruction-set architectures. It is based on ADL (Architecture Description Language) and provides more concise and manifest semantics to describe behavior of instruction set by mixing efficiency of instruction-set simulators and flexibility of RTL simulators. It exploits new timing model method based on process scheduling so it can support general timing model with cycle accuracy for large-scaled architectures usually used in SoC multimedia chip-set. According to experiments, the proposed framework was shown to be 5.5 times faster than HDL and 2.5 times faster than System-C in simulation speed so it is applicable for complex instruction-set pipelined architectures.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 F
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• pp.2193-2195
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• 1997

This paper describes a control system design for the transmission STATCON by applying a non-linear feedback. A mathematical model for the STATCON was derived by using a 3-phase equivalent circuit and its controller was designed by a numerical computation. The verification of newly designed controller was performed by EMTP simulation and scaled hardware model test. The test results show that the controller using non-linear feedback skim controls its reactive power properly without large transients.