항공기 노즈 랜딩기어의 쉬미 해석

황재혁,김두만,남창호,임경호 한국항공대학교 1993 論文集 Vol.31 No.-

본 연구를 통하여 항공기 노즈 랜딩기어의 동안정성을 지배하는 운동방정식을 유도하고, 이를 수치적으로 해석하는 프로그램을 개발하였다. 개발된 프로그램은 어떠한 초기조건 및 파라메타의 변화가 착륙장치의 동안정성에 미치는 영향을 해석하는데 매우 유용한다. 노즈 랜딩기어의 운동 방정식을 해석한 결과, 동적 불안정을 유발시키는 중요한 파라메타를 결정하였고, 이 파라메타들을 적적히 조절하면 지배장정식은 안정된 해를 갖게 된다. 그 중 대표적인 파라메타는 K?,K₃,C이다. 해의 두번째 특징으로 발산하지 않는 해 가운데서 쉬미(shimmy)현상을 나타내는 해가 있다. 쉬미현상은 비선형 시스템에서 나타나는 리미트사이클로서 고정된 진폭과 주파수를 갖고 진동하는 해를 뜻한다. 이러한 쉬미현상을 해석한 결과, 조향계통의 프리플레이(free play)가 쉬미 발생에 결정적인 원인이 됨을 확인 하였다. In this study, the equations of motion of an nose landing gear system for shimmy analysis has been derived and then the equations have been solved by numerical method. The developed program in this study is useful to evaluate the effect of the initial conditions and parameters of the nose landing gear on the its dynamic stability. It has been found that the parameters such as K?K₃,C? play the most prominent role on the dynamic stability of the nose landing gear. Shimmy is a kind of limit cycle which can be occurred in the nonlinear dynamic systems. Shimmy has been analyzed numerically in this paper. It turns out that the free play in the steering system is the most important factor to generate shimmy.

비정상 랜덤 가진력을 받는 항공기 착륙장치의 매개변수 최적설계

황재혁,박영창,이혜진 한국 항공대학교 항공산업기술연구소 2000 航空宇宙産業技術硏究所 硏究誌 Vol.10 No.-

본 논문에서는 항공기 착륙장치 동특성 해석을 통해 얻어진 중요한 매개변수를 최적 설계하는 연구를 수행하였다. 착륙장치는 선형계로 모델링하였으며, 최적설계시 성능지수는 항공기의 탑승감, 노면안정성, 완충기의 공간확보성으로 구성하였고, 설계기법으로는 확률적 최적제어기법을 사용하였다. 최적설계 전후에 대한 성능지수 및 착륙장치의 제곱평균응답 특성을 비교한 결과 성능이 매우 향상되었음을 확인할 수 있었다. The dynamic characteristics of an aircraft landing gear under nonstationary random excitation needs to be taken into account during structural design as well as to protect the cargo and on-board instrumentation. It has been found that the parameters of shock absorber played a prominent role on the dynamic characteristics. In this paper, the optimal design of the prominent parameters was conducted with respect to ride comfort, road holding, absorber stroke space using the stochastic optimal control control theory. The kinematic excitation to landing gear was modeled as a output of a first order linear spatial shaping filter to white noise excitation. The response of landing gear was found to be improved in comparison to that of original system.

The Korean Society of Gastroenterology & SIDDS 2020 : Slide Session ;K-UG-23 : Upper GI Tract ; Does Discharge Hemoglobin Affect Outcome of Patients with Acute Non-Variceal Upper Gastrointestinal Bleeding?

( Jae Min Lee ),( Hoon Jai Chun ),( In Kyung Yoo ),( Seung Joo Nam ),( Seung Han Kim ),( Hyuk Soon Choi ),( Eun Sun Kim ),( Bora Keum ),( Yoon Tae Jeen ),( Hong Sik Lee ),( Chang Duck Kim ),( Ho Sang 대한내과학회 2014 대한내과학회 추계학술대회 Vol.2014 No.1

Background: Many patients with gastrointestinal bleeding show anemia and usually need red blood cell transfusion. But clinicians are concerned about low hemoglobin affects prognosis and clinical outcome after discharge. This study aimed to assess whether discharge hemoglobin infi uence on outcomes, or not, in patient with acute non-variceal gastrointestinal bleeding. Methods: Retrospective analysis was carried out on patients who had upper gastrointestinal bleeding between January 2011 and December 2012. We analyzed the patients who had lowest hemoglobin below 10 g/dL during hospitalization. Patients with variceal bleeding, stroke, or cardiovascular disease were excluded. We divided the patients into two groups by discharge hemoglobin (Low discharge hemoglobin group; 8 g/dL = hemoglobin and compared clinical outcomes and hemoglobin level changes. Results: A total of 212 patients with upper gastrointestinal bleeding were undergone the endoscopic hemostasis during study periods. One hundred two patients were satisfi ed the inclusion criteria. fifty patients discharged with hemoglobin level under 10 g/dL and fi fty two patients discharged with hemoglobin level over 10 g/dL. Patients in low discharge hemoglobin group showed a lower consumption of pRBC and shorter hospital days than patients in high discharge hemoglobin group. Hemoglobin levelswere not fully recovered at out-patient department until 7 days after discharge. But, most patients showed hemoglobin recovery at 45 days after discharge.Conclusions: In patients with acute gastrointestinal bleeding, discharge hemoglobin between 8 to 10 g/dL was showed favorable outcomes during out-patient department follow-up. It seems to be tolerable level without additional pRBC transfusion. Our result can increase the evidence available to support restrictive transfusion strategies in patients with acute non-variceal upper gastrointestinal bleeding.

The safety and effectiveness of 2-liter polyethylene glycol plus ascorbic acid in patients with liver cirrhosis : A retrospective observational study

Lee, Jae Min,Lee, Jae Hyung,Kim, Eun Sun,Lee, Jung Min,Yoo, In Kyung,Kim, Seung Han,Choi, Hyuk Soon,Keum, Bora,Seo, Yeon Seok,Jeen, Yoon Tae,Lee, Hong Sik,Chun, Hoon Jai,Um, Soon Ho,Kim, Chang Duck Wolters Kluwer Health 2017 Medicine Vol.96 No.51

<P><B>Abstract</B></P><P>The safety of bowel-cleansing agents is an important issue in clinical practice, especially in patients with chronic diseases. Although the safety and efficacy of polyethylene glycol (PEG) has been investigated in many studies, few studies on PEG plus ascorbic acid exist. In this study, we compared the safety of 2 bowel-cleansing agents for patients with liver cirrhosis: 2-liter PEG (2 L PEG) plus ascorbic acid versus 4-liter PEG (4 L PEG). We performed a retrospective study on colonoscopy in patients with liver cirrhosis. Patients referred for colonoscopy were divided into 2 groups: 2 L PEG plus ascorbic acid (n = 105) and 4 L PEG (n = 61). Safety was assessed by comparing the clinical factors and laboratory findings as follows: blood biochemistry, electrolytes, weight change, and bowel-cleansing quality. Serum electrolytes, laboratory findings, and body weight showed no significant change between the 2 groups. There was no significant change in clinical factors before and after bowel preparation in the PEG group or the PEG plus ascorbic acid group. The acceptability and compliance of patients was better in the 2 L PEG plus ascorbic acid than the 4 L PEG group. In subgroup analysis, patients with compensated or decompensated cirrhosis showed no increased risk of electrolyte imbalances after bowel preparation. Child–Pugh scores did not influence the outcome after bowel cleansing. Successful cleansing was mostly achieved in both groups. Our analysis showed that of the use of 2 L PEG plus ascorbic acid could be a safe choice for colonoscopy in patients with liver cirrhosis.</P>

Treatment Response and Long-Term Outcome of Peginterferon α and Ribavirin Therapy in Korean Patients with Chronic Hepatitis C

( Chang Ho Jung ),( Soon Ho Um ),( Tae Hyung Kim ),( Sun Young Yim ),( Sang Jun Suh ),( Hyung Joon Yim ),( Yeon Seok Seo ),( Hyuk Soon Choi ),( Hoon Jai Chun ) 대한간학회 2016 Gut and Liver Vol.10 No.5

Background/Aims: Peginterferon plus ribavirin remains a standard therapy for patients with chronic hepatitis C (CHC) in Korea. We investigated the efficacy and long-term outcome of peginterferon and ribavirin therapy in Korean patients with CHC, particularly in relation to the stage of liver fibrosis. Methods: The incidence of sustained virological response (SVR), hepatic decompensation, hepatocellular carcinoma, and liver-related death was analyzed in 304 patients with CHC; the patients were followed up for a median of 54 months. Results: Among patients with HCV genotype 1, the SVR rate was 36.7% (18/49) and 67% (69/103) for patients with and without cirrhosis, respectively (p<0.001). For patients with non-1 HCV genotypes, the SVR rates were 86.0% (37/43) in cirrhotic patients and 86.2% (94/109) in noncirrhotic patients. SVR significantly reduced the risk of liverrelated death, hepatic decompensation, and hepatocellular carcinoma, which had hazard ratios of 0.27, 0.16, and 0.22, respectively (all p<0.05). However, despite the SVR rate, patients with advanced fibrosis were still at risk of developing liver-related complications. Conclusions: A relatively high SVR rate was achieved by peginterferon plus ribavirin therapy in Korean patients with CHC, which improved their long-term outcomes. However, all CHC patients with advanced hepatic fibrosis should receive close follow-up observations, even after successful antiviral treatment. (Gut Liver 2016;10:808-817)

국내 하지손상의 발생현황에 대한 분석

김창선 ( Chang Sun Kim ),최혁중 ( Hyuk Joong Choi ),김재용 ( Jai Yong Kim ),신상도 ( Sang Do Shin ),고상백 ( Sang Baek Koh ),이국종 ( Kug Jong Lee ),임태호 ( Tai Ho Im ) 대한외상학회 2008 大韓外傷學會誌 Vol.21 No.1

Purpose: We conducted this retrospective epidemiological study to assess the incidence and severity of lower extremity injuries in Korea Methods: For this study, we retrospectively reviewed nationwide lower-extremity injury data compiled from 2001 to 2003 based on the National Injury Database, what included National Health Insurance Corporation (NHIC), Car Insurance, and Industry Insurance data. Data were standardized in terms of demographic characteristics, region, and socioeconomic status by using NHIC data. To assess the degree of the injuries, we used the Modified Abbreviated Injury Scale (MoAIS), what has been changed from the International Classification of Disease-10 (ICD-10) code. By using the Excess Mortality Ratio-adjusted Injury Severity Score (EMR-ISS), we classified the degree of severity into four categories: mild, moderate, severe and critical. Results: From 2001 to 2003, lower extremity injuries increased slightly, with a yearly average of 2,437,335. Insurance data should that lower-extremity injuries were the most common, followed by upper-extremity injuries. Significant difference were seen in the numbers of lower extremity injuries based on gender and age. As for provinces, Seoul and Gyeongi provinces had the highest numbers of cases. Junlabukdo had the highest rate of 55,282 cases per 1 million people for standardized gender and population. The annual incidence of the insured patients with lower extrimity injuries was higher than the employer`s medical insurance contributions to the medical insurance program. Daily cases occur most often in May and June, with the lowest occurrences being in January and February. Conclusion: The result of this study shows that lower extremity injuries comprised common cause of all injuries. In addition, differences associated with gender, location and socioeconomic status were observed. Further studies are needed to find reasons and then this knowledge will allow strategies to prevent the lower extremity injuries.

Endoscopic<i>en bloc</i>resection of an exophytic gastrointestinal stromal tumor with suction excavation technique

Choi, Hyuk Soon,Chun, Hoon Jai,Kim, Kyoung-Oh,Kim, Eun Sun,Keum, Bora,Jeen, Yoon-Tae,Lee, Hong Sik,Kim, Chang Duck WJG Press 2016 WORLD JOURNAL OF GASTROENTEROLOGY Vol.22 No.23

Endoscopic submucosal tunnel dissection salvage technique for ulcerative early gastric cancer.

Choi, Hyuk Soon,Chun, Hoon Jai,Seo, Min Ho,Kim, Eun Sun,Keum, Bora,Seo, Yeon Seok,Jeen, Yoon Tae,Lee, Hong Sik,Um, Soon Ho,Kim, Chang Duck,Ryu, Ho Sang WJG Press 2014 WORLD JOURNAL OF GASTROENTEROLOGY Vol.20 No.27

<P>Endoscopic submucosal dissection is an effective treatment modality for early gastric cancer (EGC), though the submucosal fibrosis found in ulcerative EGC is an obstacle for successful treatment. This report presents two cases of ulcerative EGC in two males, 73- and 80-year-old, with severe fibrosis. As endoscopic ultrasonography suggested that the EGCs had invaded the submucosal layer, the endoscopic submucosal tunnel dissection salvage technique was utilized for complete resection of the lesions. Although surgical gastrectomy was originally scheduled, the two patients had severe coronary heart disease, and surgeries were refused because of the risks associated with their heart conditions. The endoscopic submucosal tunnel dissection salvage technique procedures described in these cases were performed under conscious sedation, and were completed within 30 min. The complete en bloc resection of EGC using endoscopic submucosal tunnel dissection salvage technique was possible with a free resection margin, and no other complications were noted during the procedure. This is the first known report concerning the use of the endoscopic submucosal tunnel dissection salvage technique salvage technique for treatment of ulcerative EGC. We demonstrate that endoscopic submucosal tunnel dissection salvage technique it is a feasible method showing several advantages over endoscopic submucosal dissection for cases of EGC with fibrosis. (C) 2014 Baishideng Publishing Group Inc. All rights reserved.</P>

유연구조물의 잔류진동제어를 위한 시간지연기법 연구

황재혁,조현권,이혜진,박영창,박진호 한국 항공대학교 항공산업기술연구소 2001 航空宇宙産業技術硏究所 硏究誌 Vol.11 No.-

본 논문에서는 유연한 부착물을 갖는 우주구조물의 회전 시 발생할 수 있는 잔류진동을 최소화하고 또한 그 응용 범위가 넓은 입력설계 방법과 등가화 된 시간 지연기법을 다루었다. 먼저 Singh과 Vadali가 제안한 제어기를 이용하여 하나의 모드에 대한 시간 지연 제어기를 설계하고 입력설계 방법과 등가화 됨을 보였다. 그리고 실제 모델에 대한 적용과 해석을 위하여 우주구조물에서 많이 사용되는 유연구조물의 운동방정식을 유도하고 해석하였고, 실험을 통하여 입력 설계 방법과 시간 지연 기법을 이용한 잔류 진동 제어에 대한 성능이 우수함을 확인할 수 있었다. In this paper, the time-delay control (TDC) design methods for command signals to minimize the induced residual vibration followed by the maneuvers of the flexible structures has been studied. The equivalence between the time-delay control and the input shaping control has been shown and TDC is applied to control the residual vibration of the flexible structure in this study. It has been shown by a series of simulation and experiments that TDC is very effective to suppress the residual vibration of flexible structure induced by its maneuvers.

Trigeminal Neuralgia Caused by Persistent Primitive Trigeminal Artery

Park, Chang Kyu,Choi, Hyuk Jai,Lee, Sung Ho,Rhee, Bong Arm The Korean Neurosurgical Society 2014 Journal of Korean neurosurgical society Vol.56 No.3

A 66-year-old man presented with typical trigeminal neuralgia (TN). Magnetic resonance angiography (MRA) revealed a primitive trigeminal artery (PTA) that came into contact with the trigeminal nerve. Based on MRA, we performed microvascular decompression (MVD). In the operational field, we confirmed the PTA location and performed MVD successfully. Postoperatively, the patient's pain subsided without any complications.