• 시스템엔지니어링학술지
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• 제12권2호
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• pp.81-90
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• 2016

The system performance of Engineered Safety Features is of utmost importance in a nuclear power plant. The human performance is identified as most critical to assurance of the optimal operability of safety systems during an emergency. The aim of this study is to determine how the performance of safety system could be evaluated using Augmented Reality technology. The paper presents a description of how a systems engineered approach could be used to develop the necessary operating conditions needed to conduct this measurement. Augmented Virtual Reality (AVR) interface technology is achieving ease of availability and widespread use in many applications today as illustrated by the launch of several AR and VR devices aimed at media consumption. As such, environments that incorporate such AVR hardware have become invaluable tools in designing human interface systems because of the high fidelity and intuitive response to natural human interaction that can be achieved [2]. The outcome of the measurement undertaken is to determine whether 1.) Operator(s) performance can be enhanced by introducing an improved cognitive method of monitoring plant information during an Emergency Operating Procedures (EOP) and 2.) In correlation, inform the performance of the diverse safety systems on the basis of human factors.

• Structural Engineering and Mechanics
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• 제14권2호
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• pp.151-170
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• 2002

Moving force identification is a very important inverse problem in structural dynamics. Most of the identification methods are eventually converted to a linear algebraic equation set. Different ways to solve the equation set may lead to solutions with completely different levels of accuracy. Based on the measured bending moment responses of the bridge made in laboratory, this paper presented the time domain method (TDM) and frequency-time domain method (FTDM) for identifying the two moving wheel loads of a vehicle moving across a bridge. Directly calculating pseudo-inverse (PI) matrix and using the singular value decomposition (SVD) technique are adopted as means for solving the over-determined system equation in the TDM and FTDM. The effects of bridge and vehicle parameters on the TDM and FTDM are also investigated. Assessment results show that the SVD technique can effectively improve identification accuracy when using the TDM and FTDM, particularly in the case of the FTDM. This improved accuracy makes the TDM and FTDM more feasible and acceptable as methods for moving force identification.

• 한국공간구조학회논문집
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• 제17권1호
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• pp.77-84
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• 2017

Vortex-induced vibration and instability vibration of tall buildings are very important fluid-structure interaction phenomenon, and many fundamental questions concerning the influence of body movement on the unsteady aerodynamic force remain unanswered. For tall buildings, there are two experimental methods to investigate the characteristics of unsteady aerodynamic forces, one is forced vibration method and the other is free vibration method. In the present paper, a free vibration method was used to investigate the unsteady aerodynamic force on tall building whose aspect ratio is 9 under boundary layer simulating city area. Wind pressures on surfaces and tip displacements were measured simultaneously, and the characteristics of tip displacements and generalized forces were discussed. It was found that variation of across-wind displacements showed different trend between the case when wind speed increases and wind speed decreases, and the fluctuating generalize forces in across-wind direction of vibrating model are larger than that of static model near the resonant wind speed and approach to the static value. And for higher wind speed range, there were two peaks in across-wind power spectra of generalize forces of vibrating model, which means that two frequency components are predominant in unsteady aerodynamic forces.

• Journal of Power Electronics
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• 제17권3호
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• pp.756-765
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• 2017

The control of the power conversion system (PCS) in a battery energy storage system has a challenge due to the existence of grid impedance. This paper studies an impedance model of an LCL-based PCS in the d-q domain. The feature of a PCS connected to a weak grid is unveiled by use of an impedance model and a generalized Nyquist criterion. It is shown that the interaction between grid impedance and the PCS destabilizes the cascaded system in certain cases. Therefore, this paper proposes a novel control method that adopts virtual resistors to overcome this issue. The improvement in the control loop leads the PCS to a more stable condition than the conventional method. Impedance measurement is implemented to verify the correctness of the theoretical analysis. Experimental results obtained from a down-scaled prototype indicate that the proposed control method can improve the performance of the PCS under a weak grid.

• 한국지하수토양환경학회지:지하수토양환경
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• 제29권1호
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• pp.1-9
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• 2024

As part of monitoring technology aimed at verifying the stability of CO₂ geologic storage and mitigating concerns about leakage, a method for measuring the pH and alkalinity of high-pressure fluid samples was established to obtain practical technology. pH measurement for high-pressure samples utilized a high-pressure pH electrode, and alkalinity was measured using the Gran titration method for samples collected with a piston cylinder sampler (PCS). Experimental samples, referencing CO₂-rich water and CO₂ geologic storage studies, were prepared in the laboratory. The PCS controls the piston, preventing CO₂ degassing and maintaining fluid pressure, allowing mixing with KOH to fix dissolved CO₂. Results showed a 6.1% average error in high-pressure pH measurement. PCS use for sample collection maintained pressure, preventing CO₂ degassing. However, PCS-collected sample alkalinity measurements had larger errors than non-PCS measurements, limiting PCS practicality in monitoring field settings. Nevertheless, PCS could find utility in preprocessing for carbon isotope analysis and other applications. This research not only contributes to the field of CCS monitoring but also suggests potential applications in studies related to natural analogs of CCS, CO₂-rock interaction experiments, core flooding experiments, and beyond.

• 한국철도학회논문집
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• 제14권3호
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• pp.211-215
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• 2011

일반적으로 음향파워는 소음원으로부터 방사되는 소음의 예측 및 평가를 위한 가장 중요한 요소 중에 하나이다. 그러나 철도차량 주행 시 이 음향파워를 직접 측정하는 것은 불가능하기 때문에 많은 연구자가 소음 레벨을 이용해서 음향파워를 계산하는 간접적인 방법을 개발하였다. 본 연구에서는 철도차량에서 방사되는 음향파워를 전동소음과 동력소음으로 분리하여 추정하는 방법을 제안하였으며, 이 추정방법의 타당성을 검증하였다. 또한 본 연구에서 제안한 방법을 이용하여 현재 국내에서 운행되는 차량(전동차, 무궁화호, KTX)의 음향파워를 계산하여 분석하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.495-496
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• 2014

The suction method is the substructure installation using the water pressure difference generated by discharging water inside the pile by the pumping operation, after the intrusion by the self-weights of a large hollow steel pipe or a concrete structure. It is known as the low-noise and low-vibration method against the general pile driven method and eco-friendly, also. Most current design and safety assessment of the support structure and considering only the static load, however, the importance of dynamic behavior becomes magnified as the size of wind power generator increases. This study measures the natural frequency of the suction pile prototype about the penetration depth as a part of basic research and analyzed the interaction between the soil and the structure.

• 스마트미디어저널
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• 제8권2호
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• pp.80-85
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• 2019

일반적으로 층간소음은 자유음장의 관점에서 데시벨(A)로 측정하고 있다. 논문에서 우리는 확산음장의 관점에서 층간진동가속도의 측정방법을 제안한다. 제안된 방법은 공동주택의 고유진동을 가속도로 측정하여 그 평균값 $20mm/s^2$를 기수의 등비수열로 나타내면, 진도계감도와 유사하게 진동체화식으로 표상할 수 있다. 이 이론을 토대로 본고는 진원지의 층간진동가속도를 HCI시스템에서 최적의 사용자 경험(UX)할 수 있도록 수식을 제시하였다.

• Wind and Structures
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• 제9권6호
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• pp.473-492
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• 2006

This paper presents numerical results of pedestrian-level wind environment around the base of a row of tall buildings by CFD. Four configurations of building arrangement are computed including a single square tall building. Computed results of pedestrian-level wind flow patterns and wind speeds are compared to previous wind tunnel measurement data to enable an assessment of CFD predictions. The CFD model uses the finite-volume method with RNG $k-{\varepsilon}$ model for turbulence closure. It is found that the numerical results can reproduce key features of pedestrian-level wind environment such as corner streams around corners of upwind building, sheltered zones behind buildings and channeled high-speed flow through a building gap. However, there are some differences between CFD results and wind tunnel data in the wind speed distribution and locations of highest wind speeds inside the corner streams. In locations of high ground-level wind speeds, CFD values match wind tunnel data within ${\pm}10%$.

• Interaction and multiscale mechanics
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• 제1권2호
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• pp.177-190
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• 2008

In this paper, both experimental measurement and theoretical analysis are used to investigate the out-of-plane resonant characteristics of a cantilevered piezoceramic plate in air and three different kinds of fluid. The experimental method, amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI), is the major technique used in this study to measure the resonant characteristics of the cantilivered piezoceramic plate. Both resonant frequencies and full-field mode shapes are obtained from this experimental technique. Numerical computations based on the finite element analysis are presented for comparison with the experimental results. Good quality of mode shapes for the cantilevered piezoceramic plate in air is obtained from the AF-ESPI technique. However, the quality decreases as the viscosity of fluids increases. From the results provided from experimental measurements and numerical computations, it is indicated that the resonant frequencies of the cantilevered piezoceramic plate in fluid decrease with the increase of the viscosity of fluids. Good agreements between the experimental measured data and the numerical calculated results are found for both resonant frequencies and mode shapes of the cantilevered piezoceramic plate in fluid.