• 센서학회지
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• 제30권5호
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• pp.349-356
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• 2021

The Korea Research Institute of Standards and Science (KRISS), a National Metrology Institute of Korea, participated in the second-round of the international key comparison CCT-K7.2021 of triple point of water (TPW) cells. For the key comparison, three TPW cells, one of which had been used in the old CCT-K7 comparison, were assigned as the national standard of the TPW. The temperature difference (ΔT) between the average of the new and old national standards and ΔT between the new national standard and the transfer standard were measured. The comparison between the new and old national standards indicated a temperature increase of 69.5 µK after both the standards were corrected for the isotopic composition. The uncertainty of the national standard of the TPW temperature was 28 µK, and the uncertainty of ΔT was 14 µK. Three aspects of improvements in the new comparison compared to the old one were noted: (1) inclusion of two quartz cells in the national standard strengthens its long-term stability; (2) the standard deviation associated with the measurement of ΔT was reduced from 21 µK to 9.6 µK; (3) and the measured immersion profile of the TPW cells was much closer to the theoretically predicted dependence.

• 센서학회지
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• 제31권6호
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• pp.448-454
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• 2022

An intralaboratory comparison of the realization of the triple-point temperature of mercury, which is defined as -38.8344℃ on the international temperature scale of 1990 (ITS-90), was conducted at the Korea Research Institute of Standards and Science (KRISS), the national metrology institute of Korea. To this end, four triple-point-of-mercury cells were compared using the resistance ratio measurement of a standard platinum resistance thermometer to validate the calibration results obtained using the triple-point-of-mercury cells at KRISS. The triple-point temperatures of all the four cells, one of which is designated as the national standard cell, were within 0.3 mK of the national standard. Based on 13 experiments on the four triple-point-of-mercury cells, the uncertainty in the comparison of the triple-point-of-mercury cells was 0.08 mK, and the uncertainty in the realization of the triple-point temperature of mercury was 0.19 mK. The results of the intralaboratory comparison validated that utilizing any of the four triple-point-of-mercury cells would result in the realization of a temperature within 0.3 mK of the average value determined by two key international comparisons for the realization of -38.3844℃ following the ITS-90.

• 한국광학회지
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• 제29권2호
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• pp.70-76
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• 2018

$0^{\circ}C$ 이하 적외선 복사온도계의 복사온도눈금 교정을 위해 기준 복사온도계 TRT2 (Transfer Radiation Thermometer 2, HEITRONICS)와 온도가변 흑체 ME30 (Model: ME30, HEITRONICS)을 사용하여 비교 교정장치를 구축하였다. 3개의 고정점(Ice ($0.01^{\circ}C$), In ($156.5985^{\circ}C$), Sn ($231.928^{\circ}C$))과 플랑크형 사쿠마-하토리식을 사용하고, $-50^{\circ}C$에서 TRT2의 내외삽 오차를 불확도에 포함시켜 TRT2의 복사온도 눈금을 교정하였다. ME30 흑체 개구에 공압으로 동작되는 뚜껑을 설치한 후 30초 동안만 뚜껑을 열고 복사온도를 측정함으로써 ME30 내에서 생기는 성에를 방지할 수 있었으며 비교 교정에 소요되는 시간도 반으로 줄일 수 있었다. $0{\sim}232^{\circ}C$ 영역 밖으로 벗어날수록 비교 교정장치의 불확도는 증가하며 $-20^{\circ}C$에서 확장 불확도는 0.26 K였다.

• Smart Structures and Systems
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• 제25권6호
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• pp.719-732
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• 2020

Real-time hybrid simulation (RTHS) which combines physical experiment with numerical simulation is an advanced method to investigate dynamic responses of structures subjected to earthquake excitation. The desired displacement computed from the numerical substructure is applied to the experimental substructure by a servo-hydraulic actuator in real time. However, the magnitude decay and phase delay resulted from the dynamics of the servo-hydraulic system affect the accuracy and stability of a RTHS. In this study, a robust stability analysis procedure for a general single-degree-of-freedom structure is proposed which considers the uncertainty of servo-hydraulic system dynamics. For discussion purposes, the experimental substructure is a portion of the entire structure in terms of a ratio of stiffness, mass, and damping, respectively. The dynamics of the servo-hydraulic system is represented by a multiplicative uncertainty model which is based on a nominal system and a weight function. The nominal system can be obtained by conducting system identification prior to the RTHS. A first-order weight function formulation is proposed which needs to cover the worst possible uncertainty envelope over the frequency range of interest. Then, the Nyquist plot of the perturbed system is adopted to determine the robust stability margin of the RTHS. In addition, three common delay compensation methods are applied to the RTHS loop to investigate the effect of delay compensation on the robust stability. Numerical simulation and experimental validation results indicate that the proposed procedure is able to obtain a robust stability margin in terms of mass, damping, and stiffness ratio which provides a simple and conservative approach to assess the stability of a RTHS before it is conducted.

• 센서학회지
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• 제17권3호
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• pp.188-194
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• 2008

For the accurate calibrations of thermometers at low temperatures, triple points of oxygen and argon have been realized using sealed-type triple point cells. The triple points were realized with both adiabatic and continuous heating methods. The resistance of three capsule-type standard platinum resistance thermometers were measured at the triple points of oxygen, argon, mercury and water for the calibrations of these thermometers in the range from $-220^{\circ}C$ to $0.01^{\circ}C$. The extended uncertainty, with the coverage factor of 2, of the calibration in this range is smaller than 1 mK.

• Journal of the Optical Society of Korea
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• 제16권2호
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• pp.145-150
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• 2012

We present a display-based visual stimulator for psychophysical and electrophysiological visual sensitivity measurements. The stimulator offers various psychophysical visual stimuli and transfers the signals from external devices along with the stimulation signals to an electrophysiological recorder. As an experimental demonstration, we perform a visual sensitivity experiment in the mesopic vision range by using the display-based stimulator. The intensity of the steady-state visual evoked potential is observed to correlate with the luminance of the flickering visual stimulation. For the psychophysically determined detection thresholds, we determine the mesopic luminance, showing agreement with the perceived brightness within the uncertainty of the luminance measurement.

• Nuclear Engineering and Technology
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• 제55권12호
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• pp.4447-4464
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• 2023

This paper focuses on the development of a new computational model of the CNESTEN's TRIGA Mark II research reactor using the 3D continuous energy Monte-Carlo code TRIPOLI-4 (T4). This new model was developed to assess neutronic simulations and determine quantities of interest such as kinetic parameters of the reactor, control rods worth, power peaking factors and neutron flux distributions. This model is also a key tool used to accurately design new experiments in the TRIGA reactor, to analyze these experiments and to carry out sensitivity and uncertainty studies. The geometry and materials data, as part of the MCNP reference model, were used to build the T4 model. In this regard, the differences between the two models are mainly due to mathematical approaches of both codes. Indeed, the study presented in this article is divided into two parts: the first part deals with the development and the validation of the T4 model. The results obtained with the T4 model were compared to the existing MCNP reference model and to the experimental results from the Final Safety Analysis Report (FSAR). Different core configurations were investigated via simulations to test the computational model reliability in predicting the physical parameters of the reactor. As a fairly good agreement among the results was deduced, it seems reasonable to assume that the T4 model can accurately reproduce the MCNP calculated values. The second part of this study is devoted to the sensitivity and uncertainty (S/U) studies that were carried out to quantify the nuclear data uncertainty in the multiplication factor k_eff. For that purpose, the T4 model was used to calculate the sensitivity profiles of the k_eff to the nuclear data. The integrated-sensitivities were compared to the results obtained from the previous works that were carried out with MCNP and SCALE-6.2 simulation tools and differences of less than 5% were obtained for most of these quantities except for the C-graphite sensitivities. Moreover, the nuclear data uncertainties in the k_eff were derived using the COMAC-V2.1 covariance matrices library and the calculated sensitivities. The results have shown that the total nuclear data uncertainty in the k_eff is around 585 pcm using the COMAC-V2.1. This study also demonstrates that the contribution of zirconium isotopes to the nuclear data uncertainty in the k_eff is not negligible and should be taken into account when performing S/U analysis.

• 대한원격탐사학회지
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• 제39권3호
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• pp.355-361
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• 2023

지구 표면에 대한 정보는 기상 및 대기 역학의 이해나 인간을 포함한 동물에 큰 영향을 미치는 극한 열현상에 대응함에 있어서 핵심적인 지구 물리량이다. 지구 영역에 대한 온도를 추정하기 위하여 위성에 탑재된 열적외 센서가 널리 활용되어 왔는데, 정밀한 활용을 위해서는 온도 추정 과정의 불확도에 대한 이해가 선행되어야 한다. 하지만 온도추정 불확도에 영향을 미치는 많은 요소 중에서 한반도 주변의 환경 하에서의 온도추정 알고리즘의 불확도 산정에 대한 연구는 미미하였다. 본 연구에서는 한반도 주변의 대기 및 해양 조건하에서 범용성이 높은 single-channel 알고리즘의 불확도를 추정하는 연구를 수행하였다. 알고리즘의 입력자료로 필요한 재분석자료(reanalysis)의 영향성을 평가하기 위하여 두 가지의 재분석자료, 즉 fifth generation of European Centre for Medium-Range Weather Forecasts reanalysis of the global climate and weather (ERA5)와 Modern-Era Retrospective analysis for Research and Applications-2 (MERRA-2)를 사용하였고, 복사전달모델은 MODerate resolution atmospheric TRANsmission (MODTRAN)을 사용하였다. MODTRAN 모의와 온도 추정 정확도 검증에 사용되는 현장 관측 수온은 한반도 인근 해역에 위치한 해양 기상 부이(buoy)로부터 획득했다. 실험 결과, 알고리즘 불확도는 대기 수증기량에 따라서 선형에 가깝게 증가하는 것을 확인하였고, 가장 건조한 조건에서는 약 0.35K 그리고 평균적으로 0.45K 가량의 불확도가 발생함을 확인하였다. 이러한 결과는 재분석자료의 종류에 상관없이 유사하게 도출되어 알고리즘이 가지는 순수한 불확도라고 추정할 수 있었다.

• 제어로봇시스템학회논문지
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• 제19권6호
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• pp.555-562
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• 2013

This paper presents the optimal array of optical mice for the accurate velocity estimation of a mobile robot. It is assumed that there can be some restriction on the installation of two or more optical mice at the bottom of a mobile robot. First, the velocity kinematics of a mobile robot with an array of optical mice is derived, which maps the velocity of a mobile robot to the velocities of optical mice. Second, taking into account the consistency in physical units, the uncertainty ellipsoid is obtained to represent the error characteristics of the mobile robot velocity estimation owing to noisy optical mouse measurements. Third, a simple but effective performance index is defined as the inverse of the volume of the uncertainty ellipsoid, which can be used for the optimization of the optimal optical mouse placement. Fourth, simulation results for the optimal placement of three optical mice within a given elliptical region are given.

• 한국농공학회논문집
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• 제54권5호
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• pp.43-47
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• 2012

A evaluation for the strength of rock includes a lot of uncertainty due to existence of discontinuity surface and weakness plain in the rock mass, so essential test results and other data for the resonable strength analysis are absolutely insufficient. Therefore, a analytical technique to reduce such uncertainty can be required. A probabilistic analysis technique has mainly to make up for the uncertainty to investigate the strength of rock mass. Recently, a artificial neural networks, as a more newly analysis method to solve several problems in the existing analysis methodology, trends to apply to study on the rock strength. In this study the unconfined compressive strength from basic physical property values of sedimentary rock, black shale and red shale, distributed in Daegu metropolitan area is estimated, using the artificial neural networks. And the applicability of the analysis method is investigated. From the results, it is confirmed that the unconfined compressive strength of the sedimentary rock can be easily and efficiently predicted by the analysis technique with the artificial neural networks.