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김남조(Nam-Jo Kim),곽동일(Dong-Il Kwak),강우람(Woo-Ram Kang),황유상(Yoo-Sang Hwang),김도형(Do-Hyung Kim),김찬동(Chan-Dong Kim),이기진(Ki-Jin Lee),소희섭(Hee-Soup So) 한국항공우주학회 2022 韓國航空宇宙學會誌 Vol.50 No.3
헬기의 능동진동제어시스템(AVCS)은 주로터로부터 발생되는 진동을 제어하며, 수동형 진동저감장치 대비 저중량으로 우수한 진동저감 성능을 발휘한다. 본 논문에서는 FxLMS 알고리즘을 기반으로 타코미터 및 가속도 센서 신호를 통해 연산된 제어명령을 하중발생기(CFG)로 전달하여 소형 민수헬기의 진동을 제어하는 소프트웨어 개발 및 검증 내용을 제시하였다. DO-178C /DO-331 표준에 따라 모델 기반 설계 기법을 통해 진동제어 소프트웨어를 개발하였으며, PILS 및 HILS 환경에서 실시간 작동 성능을 평가하였다. 특히, PILS 환경에서는 LDRA 기반 검증 커버리지를 통해 소프트웨어의 신뢰성을 향상시켰다. AVCS를 소형민수헬기에 적용하기 위해 지상/비행시험을 통해 대상 헬기 동적응답특성 모델을 획득하였다. 이를 기반으로 시스템 최적화 분석 및 비행시험을 통해 최적 성능을 발휘하는 AVCS 형상을 결정하고, STC 인증을 획득하였다. Active vibration control system(AVCS) for helicopter enables to control the vibration generated from the main rotor and has the superb vibration reduction performance with low weight compared passive vibration reduction device. In this paper, FxLMS algorithm-based vibration control software of the light civil helicopter tansmits the control command calculated using the signals of the tachometer and accelerometers to the circular force generator(CFG) is developed and verified. According to the RTCA DO-178C/DO-331, the vibration control software is developed through the model based design technique, and real-time operation performance is evaluated in PILS(processor in-the loop simulation) and HILS(hardware in-the loop simulation) environments. In particular, the reliability of the software is improved through the LDRA-based verification coverage in the PIL environments. In order to AVCS to light civil helicopter(LCH), the dynamic response characteristic model is obtained through the ground/flight tests. AVCS configuration which exhibits the optimal performance is determined using system optimization analysis and flight test and obtain STC certification.
Anticancer activity of streptochlorin, a novel antineoplastic agent, in cholangiocarcinoma
Kwak, Tae Won,Shin, Hee Jae,Jeong, Young-Il,Han, Myoung-Eun,Oh, Sae-Ock,Kim, Hyun-Jung,Kim, Do Hyung,Kang, Dae Hwan Dove Medical Press 2015 Drug design, development and therapy Vol.9 No.-
<P><B>Background</B></P><P>The aim of this study is to investigate the anticancer activity of streptochlorin, a novel antineoplastic agent, in cholangiocarcinoma.</P><P><B>Methods</B></P><P>The anticancer activity of streptochlorin was evaluated in vitro in various cholangiocarcinoma cell lines for apoptosis, proliferation, invasiveness, and expression of various protein levels. A liver metastasis model was prepared by splenic injection of HuCC-T1 cholangiocarcinoma cells using a BALB/c nude mouse model to study the systemic antimetastatic efficacy of streptochlorin 5 mg/kg at 8 weeks. The antitumor efficacy of subcutaneously injected streptochlorin was also assessed using a solid tumor xenograft model of SNU478 cells for 22 days in the BALB/c nude mouse.</P><P><B>Results</B></P><P>Streptochlorin inhibited growth and secretion of vascular endothelial growth factor by cholangiocarcinoma cells in a dose-dependent manner and induced apoptosis in vitro. In addition, streptochlorin effectively inhibited invasion and migration of cholangiocarcinoma cells. Secretion of vascular endothelial growth factor and activity of matrix metalloproteinase-9 in cholangiocarcinoma cells were also suppressed by treatment with streptochlorin. Streptochlorin effectively regulated metastasis of HuCC-T1 cells in a mouse model of liver metastasis. In a tumor xenograft study using SNU478 cells, streptochlorin significantly inhibited tumor growth without changes in body weight when compared with the control.</P><P><B>Conclusion</B></P><P>These results reveal that streptochlorin is a promising chemotherapeutic agent to the treatment of cholangiocarcinoma.</P>
Kwak, Tae Won,Kim, Do Hyung,Chung, Chung-Wook,Lee, Hye Myeong,Kim, Cy Hyun,Jeong, Young-IL,Kang, Dae Hwan Hindawi Publishing Corporation 2013 Evidence-based Complementary and Alternative Medic Vol.2013 No.-
<P>The aim of this study was to investigate the effect of the combination of vorinostat and epigallocatechin-3-gallate against HuCC-T1 human cholangiocarcinoma cells. A novel chemotherapy strategy is required as cholangiocarcinomas rarely respond to conventional chemotherapeutic agents. Both vorinostat and EGCG induce apoptosis and suppress invasion, migration, and angiogenesis of tumor cells. The combination of vorinostat and EGCG showed synergistic growth inhibitory effects and induced apoptosis in tumor cells. The Bax/Bcl-2 expression ratio and caspase-3 and -7 activity increased, but poly (ADP-ribose) polymerase expression decreased when compared to treatment with each agent alone. Furthermore, invasion, matrix metalloproteinase (MMP) expression, and migration of tumor cells decreased following treatment with the vorinostat and EGCG combination compared to those of vorinostat or EGCG alone. Tube length and junction number of human umbilical vein endothelial cells (HUVECs) decreased as well as vascular endothelial growth factor expression following vorinostat and EGCG combined treatment. These results indicate that the combination of vorinostat and EGCG had a synergistic effect on inhibiting tumor cell angiogenesis potential. We suggest that the combination of vorinostat and EGCG is a novel option for cholangiocarcinoma chemotherapy.</P>
Test and Simulation of an Active Vibration Control System for Helicopter Applications
Do-Hyung Kim,Tae-Joo Kim,Se-Un Jung,Dong-Il Kwak 한국항공우주학회 2016 International Journal of Aeronautical and Space Sc Vol.17 No.3
A significant source of vibration in helicopters is the main rotor system, and it is a technical challenge to reduce the vibration in order to ensure the comfort of crew and passengers. Several types of passive devices have been applied to conventional helicopters in order to reduce the vibration. In recent years, helicopter manufacturers have increasingly adopted active vibration control systems (AVCSs) due to their superior performance with lower weight compared with passive devices. AVCSs can also maintain their performance over aircraft configuration and flight condition changes. As part of the development of AVCS software for light civil helicopter (LCH) applications, a test bench is constructed and vibration control tests and simulations are performed in this study. The test bench, which represents the airframe, is excited using a pair of counter rotating force generators (CRFGs) and a multiple input single output (MISO) AVCS that consists of three accelerometer sensors and a pair of CRFGs; a filtered-x least mean square (LMS) algorithm is applied for the vibration reduction. First, the vibration control tests are performed with uniform sensor weights; then, the change in the control performance according to changes in the sensor weight is investigated and compared with the simulation results. It is found that the vibration control performance can be tuned through adjusting the weights of the three sensors, even if only one actuator is used.
Kwak, Min Ji,Kim, Ji Man,Shin, Il Hyung,Shin, Sang Do,Song, Kyoung Jun,Suh, Gil Joon,Kim, Hee Chan Published and distributed by Royal Society of Medi 2009 Journal of telemedicine and telecare Vol.15 No.8
<P>We developed a hands-free portable device which can provide two-way, real-time audio and video communication between hospital doctors and emergency medical technicians (EMTs) providing pre-hospital care. The device was based on an ultra mobile PC with a camera, a microphone/earphone set and a WIBRO modem for wireless Internet connection at an average data transmission rate of 1 Mbit/s. Feasibility tests were conducted in 55 real emergency situations over a period of three months at five different Rescue Centres in Seoul. Successful communication between an EMT and a doctor was achieved in 46 cases (84%). The device showed acceptable performance in terms of audio/video transmission time delays and maximum transmitted video frame rates, both outdoors, inside a building and in a moving vehicle at 70 km/h. Eight control centre staff and 11 EMTs who used the device completed a questionnaire. Despite acceptable basic performance, the device was found to be limited in terms of the contribution it made to the medical control of EMTs. However, improvements in device performance should produce higher quality pre-hospital emergency medical care in the future.</P>