• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.16 no.6
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• pp.472-477
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• 2023

In this paper, we proposes the use of Model Predictive Control (MPC) techniques to enable quadcopter drones to effectively follow paths and maintain flight safety even under dynamic external environments and disturbances. Through simulations conducted in MATLAB/Simulink, the performance of two controllers, PID and MPC, is compared in flight scenarios with disturbances. The proposed design method shows that the MPC controller, when compared to the PID controller, exhibits a difference in the Mean Squared Error between the intended flight path and the actual path of the quadcopter drone. This difference is 0.2 in performance under no disturbance, and it increases to 0.8 under disturbance, demonstrating the improved path following accuracy of the MPC controller.

• Journal of Aerospace System Engineering
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• v.18 no.3
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• pp.65-69
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• 2024

This study aimed to analyze the structural integrity of a sensor control box, a critical component for real-time monitoring of brake chamber pressure in large commercial vehicles and trailers. We utilized the computational analysis program ANSYS Workbench R2021 based on our testing conditions and vibration test specification KS R1034. Through modal analysis, we identified resonance frequencies within the frequency range of 5 Hz to 100 Hz and compared results in the frequency range of 33 Hz to 67 Hz using harmonic analysis.

• Journal of Food Hygiene and Safety
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• v.26 no.4
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• pp.315-321
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• 2011

This study was performed to investigate contamination levels of aflatoxins, the secondary metabolites produced by fungi Aspergillus flavus and A. parasiticus, in herbal medicine. Herbs is susceptible to these fungi infections through its growth harvest, transport and storage. This study determine the aflatoxin $B_1$, $B_2$, $G_1$ and $G_2$ levels by HPLC-florescence detector coupled with photochemical enhancement in 558 samples herbal medicine distributed in Korea and China. Also, We checked a transfer ratio of aflatoxins from raw herbal medicines to herbal medicine extract. Hot water extraction of herbal medicines was prepared by air pressure and high pressure condition. The analytical method for aflatoxins was validated in this method. In results recoveries of the analytical method were ranged from 67.4% to 96.2% and, limits of detection and quantitation for aflatoxins were $0.015{\sim}0.138\;{\mu}g/kg$ and $0.046{\sim}0.418\;{\mu}g/kg$, respectively. According to the results of monitoring on aflatoxins in herbal medicine, aflatoxins 1.7 ug/kg $B_1$ and 0.9 ug/kg $G_1$ were detected in only one sample of Strychni Ignatii Semen, and 0.8 ug/kg $G_1$ in Strychni Semen. About 13.6~51.3% of aflatoxins were transferred to hot water extract. Although the detected levels are under the permitted levels for aflatoxins in herbal medicine, these amounts should be considered in regard to overall daily exposure to mycotoxins.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.2
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• pp.94-101
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• 2015

To mitigate the greenhouse gas emission, many carbon capture and storage projects are underway all over the world. In Korea, many studies focus on the storage of $CO_2$ in the offshore sediment. Assurance of safety is one of the most important issues in the geological storage of $CO_2$. Especially, the assessment of possibility of leakage and amount of leaked $CO_2$ is very crucial to analyze the safety of marine geological storage of $CO_2$. In this study, the leakage of injected $CO_2$ through fault was numerically studied. TOUGH2-MP ECO2N was used to simulate the subsurface behavior of injected $CO_2$. The storage site was 150 m thick saline aquifer located 825 m under the continental shelf. It was assumed that $CO_2$ leak was happened through the fault located 1,000 m away from the injection well. The injected $CO_2$ could migrate through the aquifer by both pressure difference driven by injection and buoyancy force. The enough pressure differences made it possible the $CO_2$ to migrate to the bottom of the fault. The $CO_2$ could be leaked to seabed through the fault due to the buoyancy force. Prior to leakage of the injected $CO_2$, the formation water leaked to seabed. When $CO_2$ reached the seabed, leakage of formation water stopped but the same amount of sea water starts to flow into the underground as the amount of leaked $CO_2$. To analyze the effect of injection rate on the leakage behavior, the injection rate of $CO_2$ was varied as 0.5, 0.75, and $1MtCO_2/year$. The starting times of leakage at 1, 0.75 and $0.5MtCO_2/year$ injection rates are 11.3, 15.6 and 23.2 years after the injection, respectively. The leakage of $CO_2$ to the seabed continued for a period time after the end of $CO_2$ injection. The ratios of total leaked $CO_2$ to total injected $CO_2$ at 1, 0.75 and $0.5MtCO_2/year$ injection rates are 19.5%, 11.5% and 2.8%, respectively.

• Journal of Chest Surgery
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• v.37 no.9
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• pp.742-748
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• 2004

The On-X valve was recently introduced. It was the aim of this study to assess the safety and feasibility from the data derived from 28 patients who underwent aortic and/or mitral valve replacement with this prosthesis in National Medical Center. Material and Method： From May 1999 and May 2003, a series of 28 consecutive patients who had been implanted with 32 On-X prosthesis were reviewed, The operative procedure comprised of 12 MVR, 10 AVR and 6 DVR. The study followed the guidelines of AATS/STS. Mean follow-up was 27 months (total 04 patient-years). Result: Early ($\leq$30 days) mortality was 7.44% (2/28) and no late mortality occurred in the study. Total actuarial freedom from mortality at 2 years was 92.86$\pm$4.87% for all cases, 100% for MVR, 90$\pm$9.49% for AVR, and 83.3$\pm$1.52% for DVR. Thromboembolic event occurred in 2 MVR patients and that was the only complication; therefore, the linearized incidence of valve related complications was 3.17%/ patient-years for all cases and 6.5%/patient-years for MVR and the actuarial freedom from valve related complications at 2 years was 84.85$\pm$10.75%. Preoperatively, 24 (85.71%) patients were in NYHA functional class III or IV but postoperatively, 25 (89,29%) patients were in NYHA functional class I or II. The levels of hemoglobin, hematocrit, serum LDH, reticulocyte rate and indirect bilirubin were all within normal range at postoperative 3 month. In mitral position, the peak gradient was 6.1$\pm$1.8 mmHg and the mean gradient was 3.0$\pm$0.6 mmHg and EOA were 2.54$\pm$0.56 $m^2$, 2.39$\pm$0.73 $m^2$, 2.34$\pm$0.55 $m^2$, 2.40$\pm$0.63 $m^2$ at 27 mm, 29 mm, 31 mm, 33 mm respectively. In aortic postion, the peak gradient was 21.1 $\pm$14.12 mmHg and the mean gradient was 12.3$\pm$6.52 mmHg. Conclusion: Since there was no significant difference in the postoperative mortality, valve related complications and echocardiographic hemodynamic data compared to standard bileaflet design and since there was an improvement in the NYHA functional class and normal values of hemolytic indicators, it can be assumed that On-X valve is safe and feasible. However, accumulation of cases and long-term follow-up of this patient group is needed to establish this result.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.2
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• pp.67-75
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• 2012

Carbon-dioxide capture and storage (CCS) process is consisted by capturing carbon-dioxide from large point source such as power plant and steel works, transporting and sequestrating captured $CO_2$ in a stable geological structure. During CCS process, it is inevitable of introducing impurities from combustion, capture and purification process into $CO_2$ stream. Impurities such as $SO_2$, $H_2O$, CO, $N_2$, Ar, $O_2$, $H_2$, can influence on process efficiency, capital expenditure, operation expense of CCS process. In this study, experimental apparatus is built to simulate the behavior of $CO_2$ transport under various impurity composition and process pressure condition. With this apparatus, $N_2$ impurity effect on $CO_2$ mixture transportation was experimentally evaluated. The result showed that as $N_2$ ratio increased pressure drop per mass flow and specific volume of $CO_2-N_2$ mixture also increased. In 120 and 100 bar condition the mixture was in single phase supercritical condition, and as $N_2$ ratio increased gradient of specific volume change and pressure drop per mass flow did not change largely compared to low pressure condition. In 70 bar condition the mixture phase changed from single phase liquid to single phase vapor through liquid-vapor two phase region, and it showed that the gradient of specific volume change and pressure drop per mass flow varied in each phase.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1997.11a
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• pp.69-75
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• 1997

우리나라는 그동안 가스산업에서 고속성장을 이룩해 왔으나, 근래에는 중대가스산업사고가 빈번하게 일어나고 있다. 그건 이유로 1996년도에는 중대산업사고 예방제도가 전면적으로 실시되고 공정안전보고서를 작성하여 제출하도록 함으로서 위험성 평가의 중요성이 점차 높아가고 있으며, 위험성 평가 기법들에 대하여 여러 연구 단체에서 연구ㆍ시도되고 있다. 또한 이러한 연구ㆍ보고된 위험성 평가 기법들을 프로그램화하고 적용하려는 시도가 많이 있어 왔다. 본 연구에서는 기존에 연구ㆍ개발된 위험성 평가 기법들에 최근 컴퓨터 산업의 발달에 힘입어 각광을 받고 있는 지리정보시스템을 적용하고자 한다. 이러한 가스산업시설의 위험성 평가 시스템은 위험성을 평가하기 위해서 필요한 여러 가지 정보들을 지리정보시스템이 속성 데이터로서 저장하고 있으나, 가스산업시설에 관련된 주변의 도면들을 공간 데이터로서 저장하고 있다. 그리고 위험성 평가 시스템의 세부적인 기능을 모듈화하였다. 우선 위에 언급한 속성 데이터와 공간 데이터를 관리하는 모듈과 이러한 데이터를 가지고 사고영향 범위를 산출해내기 위한 모듈, 그리고 산출된 사고 영향 범위를 도면에 나타내는 모듈로 나뉘어져 있다. 이렇게 지리정보시스템에 구축되어 있는 도면에 위험성을 평가한 결과치를 나타냄으로서 위험성 평가 숙련자가 아니더라도 위험성 평가를 할 수 있고 결과를 분석하도록 도와 줄 수 있도록 할 수 있다. 또한 향후 재난관리시스템에서는 도면상의 도로에 교통량 가중치와 인근 소방서와 경찰서등의 위치를 관리하도록 지리정보시스템을 적용할 수 있으면, 가스시설물 관리시스템에서는 최근 대형가스사고의 대부분이 타공사에 의한 것임을 고려하여 가스배관망을 포함하여 기타 다른 지하배관망을 관리하도록 지리정보시스템을 적용할 수 있다. (중략)램프에서 좋은 광학적 특성을 얻기 위해 가장 중요한 것은 수축이 없이 방전을 확산시키는 것이다. 이를 위해서 램프구조와 구동법을 최적화하는 것이 필요하다. 또한 기체압력을 높임으로서 Xe의 여기복사를 얻을 수 있었다. 동시에 새로운 적용영역의 가능성을 탐구하는데 있다 하겠다.[C/N]의 값을 나타내었다.다.다.화 기술, 구동방법등에 대한 기술개요와 국내외 기술동향에 대하여 소개하고자 한다.었다.다._{2}$가 0.25[wt%] 첨가된 시편의 20[.deg.C]에서의 유전상수는 16,700으로 최대값을 유전손실을 1.28[%]로 최소값을 나타내었다. 또한 모든 시편은 온도 및 주파수에 따라 유전상수가 완만하게 변화하는 유전이완 특성을 나타내었다.다.수적인 물의 양에 따른 DIAION WA30의 라세미화 효율에 관하여 실험한 결과, 물의 양이 증가할수록 그 효율은 감소하였다. DIAION WA30을 라세미화 촉매로 사용하여 아이소옥탄 내에서 라세믹 나프록센 2,2,2-트리플로로에틸 씨오에스터의 효소적 DKR 반응을 수행해 보았다. 그 결과 DIAION WA30을 사용하지 않은 경우에 비해 반응 전환율과 생성물의 광학 순도는 급격히 향상되었다. 전통적 광학분할 반응의 최대 50%라는 전환율의 제한이 본 연구에서 찾은 DIAION WA30을 첨가함으로써 성공적으로 극복되었다. 또한 고체 염기촉매인 DIAION WA30의 사용은 라세미화 촉매의 회수 및 재사용이 가능하게 해준다.해준다.다. TN5 세포주를 0.2 L 규모 (1 L spinner flask)oJl에서 세포간의 응집현상 없이 부유배양에 적응,배양시킨 후 세포성장 시기에 따른 발현을 조사한 결과 1 MOI의 감염조건 하에서는 $0.6\times10^6$cell/m

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.4
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• pp.393-399
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• 2017

In a reciprocating compressor, the piston and connecting rod are important parts. Excess mechanical stress on these parts may cause damage, and broken parts are expensive and difficult to replace. Therefore, it is necessary to analyze the mechanical stress affecting durability and longevity. The main purpose of this study was to identify locations of maximum stress on pistons and connecting rods. Based on dynamic calculation of the working process of a specific air compressor, an analysis of piston and connecting rod performance has been completed. A three-dimensional model for the air compressor's pistons and connecting rods was built separately, and FEM analysis of these components was carried out using a numerical method. The pistons were loaded by pressure which was changed according to crankshaft angle without thermal boundary conditions. The simulation results were used to predict and estimate stress concentration as well as the value of this stress on pistons and connecting rods. The maximum equivalent stress calculated are over 190 MPa on pistons and 123 MPa on connecting rods at crank angle $135^{\circ}$ and $225^{\circ}$ but these are under tensile yield strength. Besides, the calculated safety factors of connecting rods and pistons is higher than 1. Moreover, the results obtained can be used to provide manufacturers with references to optimize the design of pistons and connecting rods for reciprocating compressors.

• Journal of the Korean Society for Railway
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• v.14 no.5
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• pp.433-441
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• 2011

It is a fact that the straightening of track alignment is one of the undoubted ways to improve the train speed on conventional lines, while that requires huge investment resources. Therefore, the operation of a tilting train as well as the minimum improvement of track is suggested as an effective and economical alternative way for the speed-up of conventional lines. Since a driving mechanism of tilting train is different from those of existing trains, in order to make sure its operation safety and stability on conventional line, the performance of track and roadbed must be preferentially evaluated on the conventional line. Furthermore, it is necessary to estimate the tilting-train-induced roadbed response in detail since the roadbed settlement can lead to the track deformation and even derailment. In this research, the patterns of wheel load and lateral force were monitored and analyzed through the field tests, and the derailment coefficient and degree of wheel off-loading were calculated in order to evaluate the tilting train running safety depending on the running speeds (120km~180km) on the conventional line. Moreover, roadbed pressure, settlement and acceleration were also observed as tilting-train-induced roadbed responses in order to estimate the roadbed stability depending on the running speeds. Consequently, the measured derailment coefficient and degree of wheel off-loading were satisfied with their own required limits, and all of the roadbed responses were less than those of existing high-speed train (KTX) over an entire running speed range considered in this study. As a result of this study, the tilting train which will be operated in combination with existing trains is expected to give no adverse impact on the conventional line even with its improved running speed.

• Nuclear Engineering and Technology
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• v.27 no.3
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• pp.393-402
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• 1995

The structural analysis of the reactor coolant system mainly consist of too fields. The one is the static analysis considering the impact of pressure and temperature built up during normal operation. The other is the dynamic analysis to estimate the impact of postulated events such as the seismic loads or postulated branch line pipe breaks event. Since the most important goal of the RCS structural analysis is to prove the safety of the RCS during normal operation or postulated events, a widely proven theory having enough conservatism is adopted. The load occurring on the RCS during normal operation is considered as the basic design loading condition throughout whole plant life time. The most typical characteristic of the RCS during normal operation is the thermal expansion of the RCS caused by reactor coolant with high temperature and pressure. Therefore, the exact estimation on the thermal movement of the RCS is needed to get more clear understanding on the thermal movement behavior of the RCS. In this study, the general structural analysis concept and modeling method to evaluate the thermal movement of the RCS under the normal plant operation condition are presented. To discuss the validation of the suggested analysis, analysis results are compared with the measured data which ore referred from the standardized 1000 MWe PWR plant under construction.