공동주택 비부착 외부 포스트텐션을 이용한 기초 하중전이 공법 : (인증분야 : 설계방법 및 공법)

구정모(Jeong-Mo Koo),김태호(Tae-Ho Kim),윤대영(Dai-Young Yune),김동휘(Dong-Hwi Kim) 한국콘크리트학회 2022 콘크리트학회지 Vol.34 No.5

회전익 항공기 진동흡수용 판스프링 개선연구

구정모(Jeong-Mo Koo),이광은(Gwang-Eun Lee),서정미(Jeong-Mi Seo),원태훈(Tae-Hoon Won) 한국산학기술학회 2021 한국산학기술학회논문지 Vol.22 No.9

회전익 항공기는 블레이드 회전을 이용하여 양력을 발생시키기 때문에 진동의 영향에서 자유롭지 못하다. 이러한 진동을 줄이기 위하여, 승객실과 조종석 등에 진동흡수장치가 적용된다. 그 중 진동흡수용 판스프링은 조종석 하부에 장착되며, 조종사가 느끼는 진동을 줄여주는 역할을 한다. 본 연구에서는 회전익 항공기에서 발생한 판스프링 결함에 대한 원인을 분석하고 개선안을 제시하였다. 결함 원인 분석을 위하여, 구조해석과 파단면 분석을 진행하였으며, 결함원인은 피로수명 특성 저하로 나타났다. 기존 재질을 대체할 개선 재질 2가지의 적용사례 및 타당성을 분석하여 최종 개선안을 선정하였다. 최종 개선안은 GFRP(Glass Fiber Reinforced Plastics, 유리섬유 복합재)이며, 개선안 검증을 위한 시험을 수행하였다. 판스프링 구조물에 작용하는 공진을 모사하는 가진 시험기를 이용하여 피로시험을 진행하였다. 시험방법은 S-N 피로시험으로 진행되며, 평균 피로 수명 곡선(Mean Fatigue Curve)을 생성하여 수명을 비교하였다. 판스프링 내부 고체윤활제 재질 개선을 통하여 피로강도와 수명이 기존대비 1.5배 이상 증가함을 입증하였다. A rotorcraft is not free from the effects of vibration because it generates lift using the blade rotation which is a source of vibration. To reduce the vibrations in a rotorcraft, a vibration-absorbing device is used in the passenger compartment and cockpit. Among the various vibration-absorbing devices, the vibration-absorbing plate spring is widely used and installed in the lower part of the cockpit to reduce the vibration felt by the pilot. This study analyzed the causes of plate spring defects in rotorcraft and presented suggestions for improvement. To analyze the causes of the defects, structural and fracture surface analyses were performed, and the cause of the defect was found to be the deterioration of fatigue life characteristics of the spring material. The final improvement plan was obtained by analyzing various application cases and the feasibility of using two improved materials to replace the existing materials. The final improvement proposal is the use of GFRP (Glass Fiber Reinforced Plastics), and a test was performed to verify this proposal. A fatigue test was conducted using an excitation tester that simulates the resonance acting on the plate spring structure. This test method is an S-N fatigue test, and the lifespan was estimated and compared with that of the other materials by creating a Mean Fatigue Curve. It has been proven from this study that the fatigue strength and lifespan are increased by more than 1.5 times compared to the existing ones by the improvement of the solid lubricant material inside the plate spring.

회전익 항공기 중앙동체 프레임 보강을 통한 기체구조 개선연구

구정모(Jeong-Mo Koo),서정미(Jeong-Mi Seo),최지영(Ji-Yeong Choi) 한국산학기술학회 2022 한국산학기술학회논문지 Vol.23 No.10

회전익 항공기의 중앙동체는 임무 수행을 위한 병력이 탑승하며 항전장비실, 사수부와 병력/화물부로 구성된다. 중앙동체에는 사수창과 승객실문, 계통 구성품 등이 포함된다. 항공기 각 계통의 구성품들은 양산, 운용 간 지속적으로 설계 변경을 하게 된다. 회전익 항공기는 블레이드의 회전력을 이용하여 양력을 발생시키며, 그에 따른 진동 발생은 자연스러운 현상이다. 이 항공기는 진동을 개선하기 위해 몇 가지 구성품을 추가하는 설계 변경을 수행하였다. 그 이후 예상하지 못한 위치인 중앙동체 하단 프레임에서 균열이 발생하였고, 이를 개선하기 위한 연구를 진행하였다. 본 연구의 목적은 프레임 보강을 통한 항공기의 피로파단 개선이다. 균열 발생 원인을 분석하고, 해당 부위의 응력 집중 해소를 위해 피팅(Fitting)과 스트랩(Strap)을 추가하는 방안을 채택하였다. 해당 항공기 중앙동체에 대한 유한요소모델을 만들어, 수직과 수평방향 하중을 부가하는 분석을 수행하였다. 기존 형상과, 좌우 보강재를 추가한 개선형상의 구조해석을 진행하였다. 그 결과 개선형상에서는 최대응력이 기존형상 대비 약 70% 감소함을 확인할 수 있었다. 본 연구를 통하여, 중앙동체 프레임의 응력 개선을 검증하였으며, 설계 변경에 따른 기술적 타당성을 분석하였다. 연구의 기대효과는 구조물 보강을 통한 결함 부위의 발생 응력 감소 효과이며, 응력 감소를 통해 항공기 지속 운용시 구조물 피로파단을 예방할 것으로 판단된다. The central fuselage of a rotary-wing aircraft carries troops for various missions and comprises a port station equipment room, a gunnery department, and a troop cargo department. The central fuselage houses the gunner, passenger compartment door, and system components. The components of each system of the aircraft are constantly subject to design changes between mass production and operation. The rotorcraft generates lift through the rotational force of the blades, which naturally causes vibration. The subject aircraft underwent design changes that added several components to reduce vibration. Subsequently, a crack occurred in the lower frame of the central fuselage, which was an unexpected location, and research was conducted to investigate this. The purpose of this study was to address fatigue fractures of rotary-wing aircraft through frame reinforcement. After analyzing the causes of the cracks, a method of adding fittings and straps was adopted to relieve stress concentration in the area experiencing cracks. A finite element model was created for the mid-fuselage of the aircraft, and analysis was performed to add vertical and horizontal loads. Structural analysis of the existing shape and the improved shape with the addition of left and right reinforcements was carried out. As a result, it was confirmed that the maximum stress in the improved shape was reduced by about 70% compared to the existing shape. This study verified the stress improvement in the central fuselage frame and its technical feasibility according to the suggested design change analyzed. The expected outcome of this study was the reduction of the stress generated at the defect site through the reinforcement of the structure. It is our opinion that this stress reduction will prevent the fatigue fracture of the structure during the continuous operation of the aircraft.

스테로이드와 Tamoxifen으로 후복막 섬유증 치험

구정모 ( Jeong Mo Koo ),김영훈 ( Young Hoon Kim ),홍현종 ( Hyun Jong Hong ),김혜인 ( Hye In Kim ),윤성국 ( Seong Kuk Yoon ),안원석 ( Won Suk An ),이성원 ( Sung Won Lee ),정원태 ( Won Tae Chung ) 대한신장학회 2007 Kidney Research and Clinical Practice Vol.26 No.2

Idiopathic retroperitoneal fibrosis (IRF) is a rare disease characterized by inflammatory and fibrous tissue proliferation in the retroperitoneum, which often surrounds the adjacent retroperitoneal structure to cause compressive complications such as hydronephrosis. Its pathogenesis is still unknown, but recently the association with autoimmune disease is being suggested. Although the prognosis is generally good, if diagnosis or treatment is delayed, the disease can progress to acute or chronic renal failure. In the past, surgical procedures such as ureterolysis or transpositioning of the involved ureter were the mainstay of the treatment. But recent studies using steroids, immunosuppressants and tamoxifen have reported generally good results. However, the adequate dose or duration of medical treatment and the treatment for recurred disease have not been established yet. We report a case of that retroperitoneal fibrosis recurred 1 year after 2-weeks steroids therapy. It was successfully treated with combination therapy of steroids and tamoxifen.

무부하 압축기에 의한 냉장고 기계실 소음의 능동제어

구정모(Jung Mo Koo),정의봉(Weui Bong Jeong),김태훈(Tae Hoon Kim),홍진숙(Chinsuk Hong) 한국소음진동공학회 2016 한국소음진동공학회 논문집 Vol.26 No.4

기계실 환기구를 통해 전달되는 소음의 능동제어

구정모(Jung-Mo Koo),홍진숙(Chinsuk Hong),정의봉(Weui-Bong Jeong),김태훈(Tae-Hoon Kim) 한국소음진동공학회 2015 한국소음진동공학회 학술대회논문집 Vol.2015 No.10

기계실 압축기 소음의 능동 제어를 위한 제어기 설계

구정모(Jung-Mo Koo),홍진숙(Chinsuk Hong),정의봉(Weui-Bong Jeong),배승훈,김태훈(Tae-Hoon Kim) 한국소음진동공학회 2016 한국소음진동공학회 학술대회논문집 Vol.2016 No.4

The active control of noise generated by the compressor and transmitted out of the machine room through the windows is implemented based on the FIR filter. The machine room contains most of noise sources of electric home appliances, air-conditioners and refrigerators, for example. To actively reduce the noise from the machinery room. In this paper, the transfer function of the controller for minimization of the acoustic power transmitted through the windows is mathematically formulated. The transfer functions required for implementation of the active controller are the measured. The measurements are conducted in this initial stage under the operation of the compressor with no load. For improvement of the reliability of the transfer function of the compressor to the acoustic power, additional operational measurements are performed. The real time controller is implemented based on the FIR filter using the measured transfer functions and the performance of the active controller is estimated.

항공기 와이퍼 피봇 균열 원인 분석 및 품질개선 연구

서정미(Jeong-Mi Seo),구정모(Jeong-Mo Koo) 한국산학기술학회 2022 한국산학기술학회논문지 Vol.23 No.11

항공기의 와이퍼시스템은 윈드실드 전면부에 장착되어, 호우조건에서 000 knot 까지의 비행속도에서 조종사의 시야를 확보할 수 있어야 한다. 국내에서 개발된 와이퍼시스템이 적용된 항공기에서 와이퍼 피봇 균열이 다수 확인되어, 호우환경에서 임무수행의 어려움이 발생하였다. 본 논문에서는 와이퍼 피봇의 허브 부위 균열 현상을 개선하기 위한 일련의 품질개선에 관한 연구를 수행하였다. 국산화 개발된 와이퍼시스템에서 발생한 결함에 대하여 생산, 설계, 운용 관점에서 결함요소를 식별 및 분류하고, 해당 요인을 제거하면서 결함원인을 도출하였다. 결함원인 분석을 위해 설계하중 및 체계 장착성을 검토하였고 파단면 분석을 수행하였다. 분석 결과에 따르면, 박리부식에 의한 손상이 취성파괴를 유발시켜 균열이 발생한 것으로 판단되며, 이를 방지하기 위해 내부식성이 우수한 재질로 변경하는 개선방안을 제시하였다. 개선된 재질을 적용한 와이퍼시스템을 00 FH 동안 모니터링한 결과, 현재까지 동일결함이 발생하지 않았다. 논문에서 기술된 품질개선 과정이 후속 항공기 부품국산화 개발 단계에서 유용한 참고자료로 활용되기를 기대한다. The aircraft wiper system mounted on the windshield must ensure the pilots line of sight in heavy rain at flight speeds of up to 000 knots. A number of cracks in the wiper pivot were found in aircraft during operation, causing problems when conducting missions in heavy rain. In this paper, a series of quality improvement studies was conducted to prevent cracks in the wiper pivot hub. The cause of the cracks was determined by identifying defective elements from the viewpoints of production, design, and operation, and by removing the related elements. For the cause analysis, design load and aircraft mountability were reviewed, and a fracture surface analysis was performed. According to the results, damage caused by exfoliation corrosion leads to brittle fractures that result in cracks. In addition, a plan to change to a material with excellent corrosion resistance was suggested to prevent crack recurrence.

Controller Design for Active Control of Harmonic Noise Generated by Compressor in Refrigerator

Jung-Mo Koo(구정모),Chinsuk Hong(홍진숙),Weui-Bong Jeong(정의봉),Tae-Hoon Kim(김태훈) 한국소음진동공학회 2016 한국소음진동공학회 학술대회논문집 Vol.2016 No.10

퍼지 기반 다양한 모델을 이용한 회전익 항공기 착륙장치의 위험 우선순위 평가

나성현,이광은,구정모,Na, Seong Hyeon,Lee, Gwang Eun,Koo, Jeong Mo 한국안전학회 2021 한국안전학회지 Vol.36 No.2

In the case of military supplies, any potential failure and causes of failures must be considered. This study is aimed at examining the failure modes of a rotorcraft landing system to identify the priority items. Failure mode and effects analysis (FMEA) is applied to the rotorcraft landing system. In general, the FMEA is used to evaluate the reliability in engineering fields. Three elements, specifically, the severity, occurrence, and detectability are used to evaluate the failure modes. The risk priority number (RPN) can be obtained by multiplying the scores or the risk levels pertaining to severity, occurrence, and detectability. In this study, different weights of the three elements are considered for the RPN assessment to implement the FMEA. Furthermore, the FMEA is implemented using a fuzzy rule base, similarity aggregation model (SAM), and grey theory model (GTM) to perform a comparative analysis. The same input data are used for all models to enable a fair comparison. The FMEA is applied to military supplies by considering methodological issues. In general, the fuzzy theory is based on a hypothesis regarding the likelihood of the conversion of the crisp value to the fuzzy input. Fuzzy FMEA is the basic method to obtain the fuzzy RPN. The three elements of the FMEA are used as five linguistic terms. The membership functions as triangular fuzzy sets are the simplest models defined by the three elements. In addition, a fuzzy set is described using a membership function mapping the elements to the intervals 0 and 1. The fuzzy rule base is designed to identify the failure modes according to the expert knowledge. The IF-THEN criterion of the fuzzy rule base is formulated to convert a fuzzy input into a fuzzy output. The total number of rules is 125 in the fuzzy rule base. The SAM expresses the judgment corresponding to the individual experiences of the experts performing FMEA as weights. Implementing the SAM is of significance when operating fuzzy sets regarding the expert opinion and can confirm the concurrence of expert opinion. The GTM can perform defuzzification to obtain a crisp value from a fuzzy membership function and determine the priorities by considering the degree of relation and the form of a matrix and weights for the severity, occurrence, and detectability. The proposed models prioritize the failure modes of the rotorcraft landing system. The conventional FMEA and fuzzy rule base can set the same priorities. SAM and GTM can set different priorities with objectivity through weight setting.