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- 저자 : Minchan Kim (검색결과 85 건)
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김시진(Sijin Kim),김학철(Hakchul Kim),김계환(Kyehwan Kim),박영훈(Younghoon Park),박선정(Sunjung Park),이동근(Donggeun Lee),김진곤(JinKon Kim),문희장(Heejang Moon),유영준(Youngjun You),권민찬(Minchan Kwon) 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.5
본 연구는 하이브리드 로켓 모터의 수중추진기관 적용을 위한 초기연구로 Lab-scale 하이브리드 로켓 모터를 이용하여 수중연소시험을 수행하였다. 3 m x 1 m x 1 m 크기의 수조 내 바닥면에서 55 cm 위에 연소기를 위치하여 수중연소시험을 수행하였으며 아크릴판으로 제작된 파열판(rupture disk)을 이용하여 연소실 초기 기밀을 유지하였다. 산화제는 액체아산화질소(LN2O), 연료는 HDPE를 사용하였고 KNSB 추진제를 이용하여 점화하였으며 연소시험은 총 5초간 진행되었다. 수중연소시험 결과 설계 추력에 근접하는 추력을 얻을 수 있음을 확인하였다. In this study, underwater combustion test was performed using a lab-scale hybrid rocket motor. The purpose of this study is to find out the feasibility of underwater propulsion using hybrid rocket system. Combustor was located underwater above 55cm from the bottom of water tank where the size of water tank is 3m X 1m X 1m. The combustor was sealed by installing acrylic plate rupture disk at the nozzle exit. LN2O and HDPE were used as oxidizer and solid fuel respectively, while the KNSB propellant was used as the ignitor source. The combustion duration was set to 5 seconds, and it was confirmed that the measured thrust of underwater combustion test was close to the design thrust.
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GBAS ionospheric threat model assessment for category I operation in the Korean region
Kim, Minchan,Choi, Yunjung,Jun, Hyang-Sig,Lee, Jiyun John Wiley Sons 2015 GPS SOLUTIONS Vol.19 No.3
<P> During extreme ionospheric storms, anomalous ionospheric gradients can become high enough to affect Global Navigation Satellite Systems (GNSS) Ground-Based Augmentation Systems (GBAS) and to threaten the safety of GBAS users. An ionospheric anomaly threat model for the Conterminous United States (CONUS) was developed based on extreme ionospheric gradients observed in CONUS during the last solar maximum period (2000-2004). However, in order to understand and mitigate ionosphere threats occurring in different geographical regions, ionospheric anomaly threat models have to be established for the relevant regions. To allow the certification of a GBAS ground facility in South Korea, a Korean ionospheric anomaly threat model must be determined. We describe the method of data analysis that was used to estimate ionospheric spatial gradients. Estimates of anomalous gradients in the Korean region were used to define and build an ionospheric anomaly threat model for this region. All gradient estimates obtained using Korean GNSS reference network data for potential ionospheric storm dates from 2000 to 2004 were included in this threat space. The maximum spatial gradient within this threat space is 160 mm of delay per km of user separation, which falls well within the bounds of the current ionospheric threat model for CONUS. We also provide a detailed examination of the two largest ionospheric spatial gradient events observed in this study, which occurred on November 10, 2004, and November 6, 2001, respectively. </P>
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Tussilagone Inhibits the Inflammatory Response and Improves Survival in CLP-Induced Septic Mice
Kim, Yun Kyu,Yeo, Myeong Gu,Oh, Bo Kang,Kim, Ha Yeong,Yang, Hun Ji,Cho, Seung-Sik,Gil, Minchan,Lee, Kyung Jin MDPI 2017 INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Vol.18 No.12
<P>Tussilagone, extracted from <I>Tussilago farfara</I> is an oriental medicine used for asthma and bronchitis. We investigated its mechanism of action, its inhibitory effects on lipopolysaccharide-induced inflammation in macrophages, and its impact on viability in a cecal ligation and puncture (CLP)-induced mouse model of sepsis. Tussilagone suppressed the expression of the inflammatory mediators, nitric oxide and prostaglandin E2, and the inflammatory cytokines, tumor necrosis factor-alpha (TNF-α) and high-mobility group box 1 (HMGB1), in lipopolysaccharide-stimulated RAW 264.7 cells and peritoneal macrophages. Tussilagone also reduced the activation of the mitogen-activated protein kinases and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) involved in the activation of various inflammatory mediators in activated macrophages. Moreover, tussilagone administration (1 mg/kg and 10 mg/kg) produced decreased mortality and lung injury in CLP-activated septic mice. Augmented expression of cyclooxygenase (COX)-2 and TNF-α in pulmonary alveolar macrophages of septic mice were attenuated by tussilagone administration. Tussilagone also suppressed the induction of nitric oxide, prostaglandin E2, TNF-α and HMGB1 in the serum of the septic mice. Overall, tussilagone exhibited protective effects against inflammation and polymicrobial sepsis by suppressing inflammatory mediators possibly via the inhibition of NF-κB activation and the MAP kinase pathway. These results suggest the possible use of tussilagone for developing novel therapeutic modalities for sepsis and other inflammatory diseases.</P>
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Minchan Kim,Kyunbyoung Ko 보안공학연구지원센터 2016 International Journal of Future Generation Communi Vol.9 No.9
In this paper, we develop an analytical method in order to derive approximated average symbol error expressions as tractable and closed forms in amplify-and-forward with relay receiving diversity (AFwRRD) and amplify-and-forward with relay transmission diversity (AFwRTD) systems. In AFwRRD system, each relay receives two signals from the source node and the previous relay node and transmits to the next relay or the destination node. In AFwRTD scheme, it is assumed that each relay can receive a signal from the source node or the previous relay node and transmit to the next relay and the destination node. In the proposed analytical method, we modify a dual-hop relay scheme as a single branch channel over Rayleigh fading channels. Furthermore, it is confirmed that the derived performance expressions can be applied to both AFwRRD and AFwRTD schemes. Through a numerical simulation, the analyzed performance well concurs the simulation results and it is confirmed that the performance is well analyzed in terms of the diversity order and the signal to noise ratio (SNR) gain for the different number of relays.
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Kim, Jeong-Min,Jeong, Minchan,Jin, Bong-Soo,Kim, Hyun-Soo The Korean Electrochemical Society 2014 Journal of electrochemical science and technology Vol.5 No.1
The $0.3Li_2MnO_3{\cdot}0.7LiMn_{0.55}Ni_{0.30}Co_{0.15}O_2$ cathode material was prepared via a co-precipitation method. The vapor grown carbon fiber (VGCF) was used as a conductive material and its effects on electrochemical properties of the $0.3Li_2MnO_3{\cdot}0.7LiMn_{0.55}Ni_{0.30}Co_{0.15}O_2$ cathode material were investigated. From the XRD pattern, the typical complex layered structure was confirmed and a solid solution between $Li_2MnO_3$ and $LiMO_2$ (M = Ni, Co and Mn) was formed without any secondary phases. The VGCF was properly distributed between cathode materials and conductive sources by a FE-SEM. In voltage profiles, the electrode with VGCF showed higher discharge capacity than the pristine electrode. At a 5C rate, 146 mAh/g was obtained compared with 232 mAh/g at initial discharge in the electrode with VGCF. Furthermore, the impedance of the electrode with VGCF did not changed much around $9-10{\Omega}$ while the pristine electrode increased from 21.5${\Omega}$ to $46.3{\Omega}$ after the $30^{th}$ charge/discharge cycling.
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GNSS Airborne Multipath Error Modeling Under UAV Platform and Operating Environment
Kim, Minchan,Kim, Kiwan,Lee, Dong-Kyeong,Lee, Jiyun The Institute of Positioning 2015 Journal of Positioning, Navigation, and Timing Vol.4 No.1
In the case of an unmanned aerial vehicle (UAV) equipped with a GNSS sensor, a boundary line where the vehicle can actually exist can be calculated using a navigation error model, and safe navigation (e.g., precise landing and collision prevention) can be supported based on this boundary line. Therefore, for the safe operation of UAV, a model for the position error of UAV needs to be established in advance. In this study, the multipath error of a GNSS sensor installed at UAV was modeled through a flight test, and this was analyzed and compared with the error model of an existing manned aircraft. The flight test was conducted based on a scenario in which UAV performs hovering at an altitude of 40 m, and it was found that the multipath error value was well bound by the error model of an existing manned aircraft. This result indicates that the error model of an existing manned aircraft can be used in operation environments similar to the scenario for the flight test. Also, in this study, a scenario for the operation of multiple UAVs was considered, and the correlation between the multipath errors of the UAVs was analyzed. The result of the analysis showed that the correlation between the multipath errors of the UAVs was not large, indicating that the multipath errors of the UAVs cannot be canceled out.
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Feasibility Studies for Applications of Long-Term Ionospheric Anomaly Monitor
Kim, Minchan,Bang, Eugene,Pullen, Sam,Lee, Young Jae,Lee, Jiyun IEEE 2017 IEEE transactions on aerospace and electronic syst Vol.53 No.3
<P>The results of processing preexisting ionospheric storm data are presented to demonstrate the use of the long-term ionospheric anomaly monitoring (LTIAM) tool for developing a ground-based augmentation system (GBAS) ionospheric anomaly threat model. The LTIAM not only detect the worst ionospheric gradients successfully, but also populate the current GBAS threat space with newly discovered ionospheric anomalies. As an application of LTIAM, the paper also proposes a method of utilizing its outputs to understand the distribution of anomalous spatial gradients. Examining the gradients above 50 mm/km on known storm days demonstrates that smaller (but still anomalous) gradients are far more likely than extreme gradients above 200 mm/km. The continued use of LTIAM over the current and upcoming solar peaks is discussed to estimate the likelihood of large spatial gradients.</P>
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Multi-constellation Local-area Differential GNSS for Unmanned Explorations in the Polar Regions
Kim, Dongwoo,Kim, Minchan,Lee, Jinsil,Lee, Jiyun The Institute of Positioning 2019 Journal of Positioning, Navigation, and Timing Vol.8 No.2
The mission tasks of polar exploration utilizing unmanned systems such as glacier monitoring, ecosystem research, and inland exploration have been expanded. To facilitate unmanned exploration mission tasks, precise and robust navigation systems are required. However, limitations on the utilization of satellite navigation system are present due to satellite orbital characteristics at the polar region located in a high latitude. The orbital inclination of global positioning system (GPS), which was developed to be utilized in mid-latitude sites, was designed at $55^{\circ}$. This means that as the user is located in higher latitudes, the satellite visibility and vertical precision become worse. In addition, the use of satellite-based wide-area augmentation system (SBAS) is also limited in higher latitude regions than the maximum latitude of signal reception by stationary satellites, which is $70^{\circ}$. This study proposes a local-area augmentation system that additionally utilizes Global Navigation Satellite System (GLONASS) considering satellite navigation system environment in Polar Regions. The orbital inclination of GLONASS is $64.8^{\circ}$, which is suitable in order to ensure satellite visibility in high-latitude regions. In contrast, GLONASS has different system operation elements such as configuration elements of navigation message and update cycle and has a statistically different signal error level around 4 m, which is larger than that of GPS. Thus, such system characteristics must be taken into consideration to ensure data integrity and monitor GLONASS signal fault. This study took GLONASS system characteristics and performance into consideration to improve previously developed fault detection algorithm in the local-area augmentation system based on GPS. In addition, real GNSS observation data were acquired from the receivers installed at the Antarctic King Sejong Station to analyze positioning accuracy and calculate test statistics of the fault monitors. Finally, this study analyzed the satellite visibility of GPS/GLONASS-based local-area augmentation system in Polar Regions and conducted performance evaluations through simulations.
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