• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.167.4-167
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• 2001

Accurate mathematical models of spacecraft components are an essential of spacecraft attitude control system design, analysis and simulation. Gyro is one of the most important spacecraft components used for attitude propagation and control. Gyro errors may seriously degrade the accuracy of the calculated spacecraft angular rate and of attitude estimates due to inherent drift and bias errors. In this paper, a detailed mathematical model of gyro containing the relationships for predicting spacecraft angular rate and disturbances is proposed. Stochastic model describing random drift behavior is discussed in frequency domain and time domain. In order to illustrate this approach, we analyze the behavior for Litton´s Space Inertial Reference Uint(SIRU).

• Nuclear Engineering and Technology
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• v.55 no.12
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• pp.4659-4663
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• 2023

The use of iodine S values derived using the International Commission Radiological Protection (ICRP) phantoms may introduce significant bias in internal dosimetry for Koreans due to anatomical variability. In the current study, we produced an extensive dataset of Korean S values for selected five iodine radioisotopes (I-125, I-129, I131, I-133, and I-134) for use in radiation protection. To calculate S values, we implemented Monte Carlo simulations using the Mesh-type Reference Korean Phantoms (MRKPs), developed in a high-quality/fidelity mesh format. Noticeable differences were observed in S value comparisons between the Korean and ICRP reference phantoms with ratios (Korean/ICRP) widely ranging from 0.16 to 6.2. The majority of S value ratios were lower than the unity in Korean phantoms (interquartile range = 0.47-1.28; mean = 0.96; median = 0.69). The S values provided in the current study will be extensively utilized in iodine internal dosimetry for Koreans.

• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1149-1154
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• 2010

Liquid chromatography/mass spectrometry using isotope dilution method has been established as a primary method for the measurement of cortisol in human serum. Verification of this method was accomplished by the participation in Consultative Committee for Amount of Substance-Metrology in Chemistry (CCQM) pilot study. Two levels of cortisol certified reference materials were prepared and certified by the established method. They were used as sample materials for the proficiency testing. The expanded uncertainty in the measurement of cortisol in human serum was approximately 1.2% at 95% confidence level. The results of the proficiency testing showed a good precision among the participants, but some bias to the certified values. This means that commercial field laboratories should keep traceability chain to SI unit through available reference measurement procedures and/or available reference materials.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.37 no.2
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• pp.60-68
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• 2000

This paper describes a design methodology for the CMOS current source which can be implemented in standard memory process. The proposed techniques provide a good characteristic against the power-supply variation by utilizing a self-bias circuit and the reduction of the first-order component of the temperature variation through the new temperature compensation technique and include a new current-sensing start-up circuit enabling a robust operation against the voltage noise generated during the operation of the chip. In addition to the circuit-design technology, techniques where the proposed CMOS current-reference circuit can be applied to the clocking circuits of a very high-speed DRAM are presented. The feasibility of the suggested design methodology for the CMOS current reference is demonstrated by both the analytical method and the circuit simulation.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.251-254
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• 2006

A precise real-time method of using the IGS ultra rapid products (IGU) and the GPS broadcast ephemeris to calculate the VRS orbit corrections was presented here which was suited for GPS/VRS reference station network based positioning. Test data acquired from both the SGRSN (Sichuan GPS Reference Station Network) and SCIGN (Southern California integrated GPS network) were used to evaluate the performance of the modeling techniques. The new method was proven to be more precise and reliable compared with the existing conventional network-based orbit error interpolation method. It was shown that 0.004ppm relative accuracy was reached, namely the influence from the orbit bias for the RTK positioning within 100km area can be of sub-millimeter level.

• Journal of Information Science Theory and Practice
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• v.7 no.2
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• pp.23-31
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• 2019

We report results of selection-bias-free approaches to the analysis of the impact of open access (OA) models on citation metrics. We studied reference groups of Gold and Green OA articles and the group of non-OA (Paywall) articles with the new functionality of the Web of Science Core Collection database, the InCites platform of Clarivate Analytics, and the Dimensions database of Digital Science. For each reference group we obtained the values of the percent of cited articles and citation impact and their dependence on the depth of the citation period. Different research fields were analyzed in two schemas of the InCites platform. We report the higher values and growth rates of the citation metrics: citation impact and %Cited, in the OA reference groups over the Paywall group. The Green OA articles demonstrate the highest values of citation metrics among all the OA models. Dependence of the value of citation impact on citation period follows linear law with R2 values close to 0.9-1.0. The overall annual growth rates of citation impact of the Green OA, Gold OA, and the Paywall articles, k equal, respectively, 3.6, 2.4, and 1.4 in Dimensions and 4.6, 3.6, and 2.3 in the Web of Science Core Collection. We suppose that earlier results reported for the articles in pure OA journals vs. articles in Paywall journals were affected by the high citation impact of the Green and Hybrid OA articles that could not be elucidated in the Paywall journals at that time.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.91.1-91.1
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• 2014

IGRINS (the Immersion GRating INfrared Spectrometer) is a high resolution wide-band infrared spectrograph developed by the Korea Astronomy and Space Science Institute (KASI) and the University of Texas at Austin (UT). This spectrograph has H-band and K-band science cameras, both of which use Teledyne's $2.5{\mu}m$ cutoff $2k{\times}2k$ HgCdTe HAWAII-2RG CMOS science grade detectors. Teledyne's cryogenic SIDECAR ASIC boards and JADE2 USB interface cards were installed to control these detectors. We performed lab experiments and test observations to optimize and evaluate the detector systems of science cameras. In this presentation, we describe a process to optimize bias voltages and way to reduce pattern noise with reference pixel subtraction schemes. We also present measurements of the following properties under optimized settings of bias voltages at cryogenic temperature (70K): read noise, Fowler noise, dark current, and reference-level stability, full well depth, linearity and conversion gain.

• Proceedings of the IEEK Conference
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• 2003.07b
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• pp.1093-1096
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• 2003

본 논문에서는, CMOS APS Image Sensor 내에 포함되어 회로의 면적을 줄인 새롭게 제안된 CMOS Bandgap Reference Bias Generator (BGR)를 온도 및 방사능에 대한 응답을 실험하였다. 제안된 BGR 회로의 설계 목표는 V/sub DD/는 2.5V이상이고, V/sub ref/는 0.75V ± 0.5mV 마진을 가지게 하는 것이다. 제안된 BGR회로는 Level Shifter를 갖는 Differential OP-amp단과 Feedback-Loop를 가지는 Cascode Current Mirror를 사용하여 저전압에서도 동작을 가능하게 하였으며, 높은 출력저항 특성을 가지도록 하였다. 제안된 BGR회로는 하이닉스 0.18㎛ ( triple well two-poly five-metal ) CMOS 공정을 이용하여 Test Chip을 제작하였다. 온도의 변화와 Co-60 노출조건 하에서 Total ionization dose (TID) effect된 BGR회로의 V/sub ref/를 측정하여, 이를 평가하였다. 온도에 대한 반응은, 25℃ 일 때의 V/sub ref/에 대해, 각각 45 ℃에서 0.128%. 70℃에서 0.768% 변화하였다. 그리고 온도가 25℃일 때 50krad와 100krad의 방사능을 조사 하였을 경우, V/sub ref/는 각각 2.466%, 그리고 4.612% 변화하였다.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.9
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• pp.49-56
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• 1998

In this paper, a design of bias circuit in temperature independent voltage detect circuit is proposed. In order to realize this intention, we are used the differences in temperature coefficient of thermal voltage, resistor and transistor forward voltage(V$\sub$BE/) which is consisted in comparator. That is, It is realized by compensating the difference of temperature coefficient due to using components with each different temperature coefficient. As well, reference voltage of the circuit is accomplished by the difference of transistor forward voltage($\Delta$V$\sub$BE/) in comparator. In using reference voltage, resistor and V$\sub$BE/ Multiplier, we can design detect voltage of the circuit. In order to test operation of proposing circuit, we manufactured IC. Then, we measured operating characteristics and capability of the circuit by using HP4145B and temperature chamber. The result, we could obtain the good variation of temperature from -0.01 %/$^{\circ}C$ to -0.025 %/$^{\circ}C$.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.379-395
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• 2021

For the complicated structural details in ships and offshore structures, the traditional hotspot stress approaches are known to be sensitive to the element variables of element topologies, sizes, and integration schemes. This motivated to develop a new approach for predicting reasonable hotspot stresses, which is less sensitive to the element variables and easy to be implemented the real marine structures. The three-point bending tests were conducted for the longitudinal attachments with the round and rectangular weld toes. The tests were reproduced in the numerical simulations using the solid and shell element models, and the simulation technique was validated by comparing the experimental stresses with the simulated ones. This paper considered three hotspot stress approaches: the ESM method based on surface stress extrapolation, the Dong's method based on nodal forces along a weld toe, and the proposed method based on nodal forces perpendicular to an imaginary vertical plane at a weld toe. In order to study the element sensitivities of each method, 16 solid element models and 8 shell element models were generated under the bending and tension loads, respectively. The element sensitivity was analyzed in terms of Stress Concentration Factors (SCFs) in viewpoints of two statistical quantities of mean and bias with respect to the reference SCFs. The average SCFs predicted by the proposed method were remarkably in good agreement with the reference SCFs based on the experiments and the ship rules. Negligibly small Coefficients of Variation (CVs) of the SCFs, which is measure of statistical bias, were drawn by the proposed method.