• Structural Engineering and Mechanics
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• v.82 no.6
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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.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.6
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• pp.1055-1060
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• 2020

This study is a study on the analysis and measurement of the radar cross-sectional area of a miniature aircraft. Radar cross-sectional area for miniature aircraft in advance were analyzed using an electromagnetic analysis tool, and an actual miniature aircraft was manufactured and measured in an anechoic chamber. When measuring, the old model was used as reference data for RCS(radar cross section) characteristics and applied to the test result data of the actual reduced model. The measurement method improved the accuracy of the measurement by applying time gating to remove the influence on the components scattered inside the anechoic chamber. The RCS test results of the reduced model showed relatively high RCS characteristics in the microwave band, as the previous analysis results. In the future, we plan to utilize the method of RCS analysis and measurement for the target of the radar in the VHF(Very High Frequency)/UHF(Ultra High Frequency) band with a relatively large wavelength.

• Journal of Mechanical Science and Technology
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• v.20 no.1
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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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• v.19 no.2
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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.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.5
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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.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.7
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• pp.705-711
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• 2003

In this Paper, 2${\times}$100 $\mu\textrm{m}$ AlCaN/GaN HEMT's(on sapphire substrate) large signal model including thermal effect was extracted. An equation based empirical model was employed to make large signal model for convergence and high speed. Pulsed I-V measurement was performed to extract thermal resistance and capacitance. Power amplifiers with 9 mm and 15 mm AlCaN/GaN HEMTS were designed using scaled modeling results of 2${\times}$100 $\mu\textrm{m}$ device respectively. From comparisons between measured and simulated data, the model considering of thermal effects gave better agreement than without one. It demonstrates that thermal modeling must be performed for power amplifier that uses large size transistors.

• Nuclear Engineering and Technology
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• v.53 no.9
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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.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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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.

• Proceedings of the IEEK Conference
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• 2005.11a
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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.

• Proceedings of the KIEE Conference
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• 1997.07f
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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.