• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.3
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• pp.29-35
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• 1997

The megastructure combined with the modular concept is an effcient structural system adequate for ultra-tail buildings for the future. An ingeneous structural control system can be developed by separating the internal subframe in one or many modules from the external megaframe, thus taking advantage of the effect of tuned mass dampers without adding any aditional mass. This so called mega-subcontrol system is generally modeled by a 20DF system for parametric study and for finding optimal values of the parameters. In this study the equation of motion for the system is obtained frist and the preconditions for the simplified modeling are investigated. Finally the optimal value for the subsreucture strffness is fomputed with given mass and damping ratios and transfer functions for responses are abtained for white noise ground exitation to verify the effectiveness of the mega-subcontrol system.

• Journal of Aerospace System Engineering
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• v.12 no.2
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• pp.7-14
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• 2018

In this study, a new check valve was studied to improve the load pressure of a brake system with a small piezoelectric-hydraulic pump. During the pressurization process, the steady-state pressure at the load is affected by the ratio of the cross-sectional area of the check valve the chamber pressure and load pressure. Since the flow path cover of the check valve is made wider than the cross-sectional area of the output flow to prevent backflow, a method of reducing the area ratio is proposed for a higher load pressure by mounting an additional mass to a thin plate spring type check valve. To identify the effect of mounting an additional mass to the existing check valve on the load pressure, a simple brake system with a small piezoelectric-hydraulic pump was modeled using a commercial code AMESim. The AMESim modeling was verified by comparing the simulation results with the experimental results of the pump the existing check valve. The additional mass was added to the verified AMESim modeling and higher load pressure was able to be obtained through simulation. The 35% performance improvement in load pressure identified by carrying out pressurization test of the brake system after adopting the new check valve the small piezoelectric-hydraulic pump.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.1
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• pp.47-54
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• 2019

An improved method of spectrum detection algorithm for mass spectrum analysis system is proposed. In the conventional spectrum detection algorithm that utilizes the results of the linear approximation and quadratic curve fitting on the ion signal block of each mass index, it is possible to reduce the detection error in the mass spectrum detection by further improving the condition of eliminating the invalid ion signals. Also, the proposed method can reduce the estimation error of the peak value of the mass spectrum by using the result of quadratic curve fitting for the effective ion signal block in which the peak position error is corrected. To evaluate the effectiveness of the proposed method, computer simulations were carried out step by step using the measured ion signal. Also, by comparing the rate of false detection for several inputs, the proposed method showed better detection performance than the conventional method.

• Journal of Conservation Science
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• v.26 no.2
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• pp.133-142
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• 2010

This paper focused on desalination method for the underwater archaeological ceramics. The desalination method applied in this study takes additional conditions such as the amount of desalting water, temperature, and agitation conditions and compares the effects of desalt process. The result of efficiency rate appears that the twenty-times of the object weight of desalting water is more effective than that of ten-times one, but shows less economic compared to the cost. In addition, the research shows that the efficiency rate has been improved around 20 to 30 %, yet such improvement is not taken into account as an effective result considering the risk of damage from the physical and chemical impact and the consumption of energy in applying additional method.

• Journal of Korean Society on Water Environment
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• v.23 no.5
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• pp.683-688
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• 2007

Water flow into unsaturated soils is most often modeled by Richards equation consisting of the mass conservation law and Darcy's law. Three standard forms of Richards equation are presented as the head (${\Psi}$)-based form, the moisture content (${\theta}$) based form, and the mixed form. Numerical solutions of these partial differential equations with highly nonlinear terms can cause poor results along with significant mass balance errors. The numerical solution based on the mixed form of Richards equation is known that the mass is perfectly conserved without any additional computational efforts. The aim of this study is to develop fully implicit numerical scheme of Richards equation for one-dimensional vertical unsaturated flow in homogeneous soils using the finite difference approximation, and then to perform sensitivity analysis of infiltration to the variations in the unsaturated soil properties and to different soil types.

• The Journal of the Acoustical Society of Korea
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• v.26 no.6
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• pp.276-285
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• 2007

In this paper it was discussed and compared measured loudspeaker impedance curve with ones reconstructed by TS parameters estimated using four kinds of parameter estimation methods developed in frequency domain. Frequency dependent parameters were introduced and derived using least square error minimization technique. For known dynamic mass TS parameter estimation methods were reviewed and also proved non-uniqueness of these parameters by simulation method. Minimum phase transformation was adopted to derive phase information from magnitude of loudspeaker electrical impedance curve measured by one channel analyzer.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.569-574
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• 1997

프랑스 가압경수형 원전인 울진 1,2호기 cavity의 격납용기 직접가열에 대한 특성을 분석하기 위하여 노심 용융물 고압분출 실험 연구를 수행하였다. 울진 1,2호기 격납건물은 국내의 Westinghouse와 CE형 원전과 달리 원자로용기 하부 cavity내 수평통로에 의한 출구가 없어 원자로용기 외곽의 환형통로를 통해 cavity와 격납건물 상부 대기와 직접 연결되어 있는 특성을 가지고 있다. 본 연구에서는 환형통로 면적, 파손 직경 용융물 질량 등에 따라 원자로용기 압력을 변화시키면서 용융물을 물, 증기를 질소기체로 각각 모의하여 실험을 수행하였다. 실험결과, 노심용융물 고압분출에는 원자로용기 파손 직경이 많은 영향을 미치는 것으로 나타났고 환형통로 면적과 용융물 질량은 큰영향을 미치지 않는 것으로 나타났다. 또한 환형통로 면적의 감소는 노심용융물 고압분출시 cav의 압력을 다소 상승시키는 결과를 보여주었다. 본 실험 연구에서 노심용융물 고압분출에 많은 영향을 미치지 않는 것으로 나타난 환형통로 면적에 대해서는 종합적으로 분석하는 추가 실험 이 필요하다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.2
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• pp.644-650
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• 2010

In this paper, an experimental study is performed in order to determine the effects of interaction between vehicle and structure. For this purpose a wheel tracking machine and an adequate precast concrete deck single span bridge are designed. Results presented in the paper show that interaction between vehicle and structure produce additional effects on dynamic behavior of structure including reversal and contrary behavior.

• Journal of the Korean Electrochemical Society
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• v.19 no.3
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• pp.63-68
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• 2016

$Li_4Ti_5O_{12}$ is prepared through a solid-state reaction between anatase $TiO_2$ and $Li_2CO_3$ for the negative electrode active materials in quick-charging lithium-ion batteries. The small amount of carbon black (0, 0.5, 1.0, and 3.0 wt%) is added for the reduction of powder agglomeration during heat-treatment. As the amount of the added carbon black increases, the tap density of $Li_4Ti_5O_{12}$ powder gradually decreases. Furthermore, the $Li_4Ti_5O_{12}$ powder prepared with 1.0 wt% of carbon black shows the highest sieved fraction at the powder classification by 325 mesh standard sieve. The $Li_4Ti_5O_{12}$ powders with various contents of carbon black are almost same at the rate capability for the negative electrode materials in lithium-ion batteries.

• Journal of Aerospace System Engineering
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• v.13 no.6
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• pp.43-51
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• 2019

The aircraft vertical acceleration from the excitation of the road surface in the taxing mode is a main factor with a negative effect on the boarding quality of pilots and passengers. In this paper, we propose an appropriate control method to improve the boarding quality of the MR damper landing gear. The proposed control method is Skyhook Control Type 2, which feeds the aircraft vertical acceleration back in addition to the aircraft vertical velocity. Since Skyhook Control Type 2 factors the velocity and acceleration of the upper mass, it can be expected to exceed the control performance of the existing Skyhook Control that factors only the upper mass velocity. For the simulation, the bumper type road surface was selected as a ground surface, and the landing gear model constructed with RecurDyn and the controller designed with Simulink were co-simulated. The control effect of Skyhook Control Type 2 was verified by comparing and analyzing the RMS and maximum value of the upper mass acceleration according to the taxing speed and control method.