• 대한기계학회논문집A
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• 제35권9호
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• pp.1119-1129
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• 2011

쇼트피닝(shot-peening) 처리를 한 베어링강의 고사이클 피로거동을 연구하였다. 열처리한 베어링강(JISSUJ2) 시험편과 열처리 후 쇼트피닝 표면가공을 추가한 시험편을 사용해 회전굽힘피로시험을 수행하고 파단 된 시험편의 파면을 분석하였다. 시험편의 피로파괴는 표면 결함에서 비롯된 표면 파괴와, 내부의 비금속개 재물에서 비롯된 내부형 파괴의 두 종류로 발생하였다. 내부 파괴의 경우 비금속 개재물 주변에 어안(fisheye) 모양의 파괴양식이 관찰되었다. 개재물은 표면으로부터의 깊이와 형상에 따라 피로 수명에 큰 영향을 주었다. 쇼트피닝 가공을 한 베어링강은 저사이클 하중영역 및 고사이클 하중영역에서 모두 피로수명이 향상되었으며, 하중이 작아질수록 피로수명의 개선은 더욱 커졌다. 또한 2 모수 와이블(Weibull) 분포를 이용하여 베어링강의 확률-응력-수명 (P-S-N) 곡선을 구하여 신뢰도 높은 피로수명 예측을 하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2000년도 추계학술대회 논문집
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• pp.74-77
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• 2000

Porthole die extrusion has a great advantage in the forming of hollow section tubes difficult to produce by conventional extrusion with a mandrel on the stem. Because of the complicated structure of die assembly, extrusion process as a forming of hollow section tubes has been investigated experimentally Therefore, analytic approaches that are useful in profitable die design and in the improvement of productivity are inevitably demanded Welding strength is affected by many parameters, which are such as extrusion ratio, extrusion speed, die shape, porthole number, bearing length, billet temperature and mandrel shape. In this paper, the parameters, which are such as billet temperature, bearing length and tube thickness, are examined. The welding pressures are examined through 3D simulation of non steady state and compared with experimental results.

• Smart Structures and Systems
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• 제1권2호
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• pp.121-140
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• 2005

This paper presents a systematic investigation of the effect of sensor location on the data quality and subsequently, on the effectiveness of machine health monitoring. Based on an analysis of the signal propagation process from the defect location to the sensor, numerical simulations using finite element modeling were conducted on a bearing test bed to determine the signal strength at several representative sensor locations. The results showed that placing sensors closely to the machine component being monitored is critical to achieving high signal-to-noise ratio, thus improving the data quality. Using millimeter-sized piezoceramic plates, the obtained results were evaluated experimentally. A comparison with a set of commercial vibration sensors verified the developed structural dynamics-based sensor placement strategy. It further demonstrated that the proposed shock wave-based sensing technique provided an effective alternative to vibration measurement, while requiring less space for sensor installation.

• 한국안전학회지
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• 제18권2호
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• pp.6-15
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• 2003

A method is presented for diagnosing the converter bearings by using acoustic emission. The flaking mechanism causing the large-scale bearing for furnace to flaw is investigated and a possibility of defect is verified by Finite Element method. he diagnosis logic is proposed fir detecting the flaw of a non-continuous rotating machine. It is proved that the acoustic emission energy can be used as a representative parameter for an acoustic event. Applying the method to the tilting bearings for steel mill in operation, the effectiveness of this logic is evaluated. It is shown that AE signal is generated only when the bearing is tilting, and the trend analysis can be focused upon this process.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 추계학술대회논문집; 한국과학기술회관; 6 Nov. 1997
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• pp.29-35
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• 1997

This research presented a frequency analysis method to analyze NRRO in a computer hard disk drive. RRO was proved to be the harmonics of rotational frequency. The frequency components of NRRO is the subtraction of the harmonics from TIR in frequency domain, so that NRRO in time domain can be obtained by Fourier inverse transformation of NRRO in frequency domain. This method can make the experiments simple without the index signal indispensable to time domain analysis. This research also shows that NRRO is caused by the defect frequencies of ball bearing. Even though the excitation force of ball bearing is independent of the rotational speed, the amplitude of NRRO is magnified near the resonance frequencies of the spindle motor. NRRO in axial direction is almost twice bigger than that in radial direction, because the spindle motor has smaller stiffness in axial direction.

• Archives of Reconstructive Microsurgery
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• 제11권1호
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• pp.1-10
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• 2002

Purpose : To analyze the clinical results of free vascularized osteocutaneous fibula graft to tibial defect combined with soft tissue defect and infection. Materials and Methods : In the retrospective study of 51 consecutive cases of vascularized osteocutaneous fibular graft, the length of the grafted fibula, size of the skin flap, anastomosed vessels, ischemic time of the flap, time for union, hypertrophy of fibula and the complications were evaluated. Results : Initial bony union of the grafted fibula was obtained at 3.74 months after operation, except 4 cases of nonunion and delayed union. The weight bearing without external supports was possible at 18 months after operation in average. The fracture of grafted fibula was most common complication(16 cases). Conclusion : The vascularized osteocutaneous fibula graft provided satisfactory bony union and functional results in the cases not responsible for conventional treatment methods.

• Archives of Reconstructive Microsurgery
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• 제15권2호
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• pp.111-116
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• 2006

An infection after total knee arthroplasty has many complications such as severe bone defect, skin and soft tissue problems, devastated general condition, so arthrodesis is preferred as treatment option. However, poor bony contact due to severe bone defect and inadequate conditions of the soft tissue often cause nonunion or severe limb shortening after arthrodesis. More over these conditions, it is not easy to choose appropriate fixative devices. In these situations, the arthrodesis using vascularized fibular graft can be the solution. Vascularized fibular graft (VFG) can playa role as a suitable material for the treatment of bone defects. And VFG can overcome poor blood circulation caused by scar tissues, and can be relatively more durable and adequate length. In the long term, VFG can be hypertrophied by weight bearing, and will give mechanical stablility. The purpose of the paper is to report the successful results of arthrodesis using VFG in a patient who got extensive bone defect after failed revision total knee arthroplasty with infection.

• 대한두개안면성형외과학회지
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• 제18권2호
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• pp.112-116
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• 2017

The ideal scalp reconstruction involves closure of the defect with similar hair-bearing local tissue in a single step. Various reconstructions can be used including primary closure, secondary healing, skin grafts, local flaps, and microvascular tissue transfer. A 53-year-old female patient suffered glioblastoma, which had recurred for the second time. The neuro-surgeons performed radial debridement and an additional resection of the tumor, followed by reconstruction using a serratus anterior muscle flap with a split-thickness skin graft. Unfortunately, the flap became completely useless and a bilateral rotation flap was used to cover the defect. Two month later, seroma with infection was found due to recurrence of the tumor. Additional surgery was performed using multiple perforator based island flap. The patient was discharged two weeks after surgery without any complications, but two months later, the patient died. Radical surgical resection of tumor is the most important curative option, followed by functional and aesthetic reconstruction. We describe a patient with a highly malignant tumor that required multiple resections and subsequent reconstruction. Repeated recurrences of the tumor led to the failure of reconstruction and our strategy inevitably changed, from reconstruction to palliative treatment involving fast and stable wound closure for the patient's comfort.

• Archives of Reconstructive Microsurgery
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• 제14권2호
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• pp.144-151
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• 2005

Purpose: Disaster as traffic accident, industrial disaster, high voltage electrical bum and flame burn of extremity have a destructive effect because of the involvement of deep structure. Generally, such injury may result in decreased function or loss of limb. In this study the successful use of the combined scapular/parascapular flap as microsurgical transfer to cover extensive defect of electrical and flame bum is reported. Material and Method: Between January 2000 and June 2001, the combined scapular and parascapular flap was used for the coverage of soft tissue defect for 7 patients were admitted to our department with high voltage electrical bum and flame burn. The recipient site were the wrist joint in 2 cases, the forearm in 1 case, the ankle joint in 1 case, the foot dorsum in 1 case, the heel in 1 case. Result: Flap survival was complete in all patients. The result of flap coverage for these deep wound was successful. Conclusion: The advantages of scapular/parascapular combined flap were coverage of the large defect, easy shaping of the flap to fit the required three dimensional configuration around the joint, non hair bearing skin of uniform thickness, minimal donor site morbidity.

• Archives of Reconstructive Microsurgery
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• 제14권1호
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• pp.18-23
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• 2005

Purpose: To report the results and the efficacy of the sensory bearing scapular free flap which is known as non-sensible flap. Materials and Methods: Authors underwent 24 cases of sensory bearing scapular free flap to the hands and feet from March 1995 to November 2002. average follow-up period was six year three months. The used flaps were a ordinary scapular flap in fifteen cases, and a parascapular flap in nine. Sensibility of the flaps were checked every one month. Actual sensory evaluation was mostly depends on objective feeling of the patients. Two point discrimination test was performed in all cases. Results: 23 flaps had good skin circulation after microvascular anastomosis among 24. Objective deep touch sensation were observed about three months later after the operation in three cases, between three and six months in nine. In three case whose results were excellent than others, two point discrimination was 2.7 cm at last follow-up. Most of the sensory recovery is confined in deep touch, temperature and light touch sensation was recovered limitedly in 3 cases during our follow-up period. Conclusion: Authors can propose that sensory bearing free scapular flap was considered as one of useful methods for the reconstruction to hand with soft tissue defect and mutilating hand.