• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 춘계학술발표대회
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• pp.15.1-15.1
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• 2009

Nano transfer printing and micro contact printing is well known printing method based on soft lithography which uses conformal soft elastomer with designed surface relief structures. Here I introduce another class of novel 3D nanofabrication technique by using the same elastomer but in a different manner. The approach, which we refer to as proximity field nanopatterning, uses the surface-reliefed elastomers as phase masks to pattern thick layers of transparent, photosensitive materials. Aspects of the optics, the materials, and the physical chemistry associated with this method are outlined. A range of 3D structures illustrate its capabilities, and several application examples demonstrate possible areas of use in technologies ranging from microfluidics to photonic materials to density gradient structures for chemical release and high-energy density science.

• 전력전자학회논문지
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• 제27권3호
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• pp.180-191
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• 2022

In this paper, a single-stage alternating current (AC)-DC converter is proposed for the automated-guided vehicle wireless charging system. The proposed converter is capable of soft-switching under all input voltage (VAC: 220 Vrms ± 10%), load conditions (0-1 kW), and air gap changes (40-60 mm) by phase control at a fixed switching frequency. In addition, controlling a wide output voltage (Vo: 39~54 VDC) is possible by varying the link voltage and improving the input power factor and the total harmonic distortion factor. Experimental results were verified by making a prototype of a 1-kW wireless power charging system that operates with robustness to changes in air gaps.

• 소성∙가공
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• 제15권6호
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• pp.436-440
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• 2006

A rapid tooling (RT) method fur the resin transfer molding (RTM) have been investigated. We fabricated a curved I-beam to verify the method. After creating a three-dimensional CAD model of the beam we fabricated a prototype of the model using a rapid prototyping (RP) machine. A soft mold was made using the prototype by the conventional silicone mold technique. The procedure and method of mold fabrication is described. The mold was cut into several parts to allow easier placement of the fiber preform. We conducted the resin transfer molding process and manufactured a composite beam with the mold. The preform was built by stacking up eight layers of delicately cut carbon fabrics. The fabrics were properly stitched to maintain the shape while placement. The manufactured composites beam was inspected and found well-impregnated. The fiber volume ratio of the fabricated beam was 16.85%.

• 전자공학회논문지B
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• 제33B권10호
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• pp.148-156
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• 1996

Increasing the switching frquency is essential to achieve the high density of switched mode power supplies, but this leads to the increase of switching losses. A number of new soft switching converters have been presented ot reduce switching losses, but most of them may have some demerits, such as the increase of voltage/current stresses and high conduction losses. To overcome these problems, the ZVT-PWM converter has recently been presented. in this paper, the operation characteristics of the ZVT-PWM boost converter is analyzed, and the steady-states (DC) and small-signal model of this converter are derived and analyzed, and then the transfer functions of this converter are derived. The transfer functions of ZVT-PWM boost converter are similar to those of the conventional PWM boost converter, but the transfer characteristics are affecsted by te duty ratio and the switching frequency.

• Archives of Reconstructive Microsurgery
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• 제10권2호
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• pp.154-162
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• 2001

Diabetic foot ulcer is a serious complication which result from long-standing diabetes. Especially, severe infected diabetic foot ulcer results in unwanted lower extremity amputation. The diabetic patient is considered the relative contraindication for microsurgery because of the severe peripheral vascular disease. Recently, microvascular free tissue transfer technique applied to diabetic foot ulcer. It is well known that free tissue transfer provides immediate soft tissue coverage and control of infection. So it is possible that preservation of the lower extremity through free tissue transfer. A retrospective study of diabetic patients who had infected foot ulcer from 1999 to 2000 with foot defects reconstructed with free tissue transfer were reviewed. Thirteen patients were studied with mean follow-up of 12.7 months. There were two deaths during follow-up period. There were two failures after free flap surgery. All eleven survived patients were ambulatory. There was no recurrence of ulcer. No patient need amputation above the ankle joint. We have found that free tissue transfer for infected diabetic foot ulcer is very effective surgical technique. Careful patient selection and regular follow-up is important.

• Archives of Reconstructive Microsurgery
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• 제10권2호
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• pp.75-80
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• 2001

Purpose : We have evaluated the morbidity of donor site after transfer of free fibular osseous and osteocutaneous flap to defect site of bone and soft tissue due to chronic osteomyelitis of long tubular bone, open fracture with bony defect, bone or soft tissue tumor and congenital anomaly. Materials and methods : The 54 cases of 79 cases to be carried out from May, 1982 to May, 2001 which could be followed up were reviewed. There were forty nine in male and five in female. The mean age was 35(4 to 66)years old and mean follow up period is 21.3 month(12 to 72). We have retrospectively analyzed the various postoperative complications such as compartment syndrome, donor site infection, skin defect, hypesthesia, hammer toes, ankle instability and activity of daily living by help of questionnaire, telephone, physical examination, follow up x-ray study and chart. Results : In the total 54 cases the medication period for pain control after operation were classified into three groups under 2 weeks(49 cases), from 2 weeks to 6 weeks(3 cases) and over 6 weeks(2 cases). The postoperative morbidity were occurred in total 12 cases(compartment syndrome: 0, infection : 2, skin defect: 1, hypesthesia: 5, hammer toe: 2 ankle pain: 2 discomfort in activity of daily living: 0), and also the morbidity rates of donor site were 23.5% in osseous flap and 21.6% in osteocutaneous flap were occurred. There was no statistical significonce in morbidity between osseous and osteocutaneous free fibular flap transfer(P>0.05). Discussion : In general the morbidity of free fibular flap transfer was relatively high but it did not have any effect on daily activity of living. We think that the meticulous operation technique, detailed wound care and early range of motion exercise will reduce the morbidity of donor site of flap.

• 한국지반신소재학회논문집
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• 제9권3호
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• pp.9-18
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• 2010

토목섬유보강 성토지지말뚝시스템에서의 하중전이 특성을 규명하기 위하여 일련의 모형실험을 실시하였다. 모형토조에 단독캡 말뚝을 설치하고, 토목섬유를 포설한 후 성토를 실시하였다. 연약지반 대체재료로서 스펀지고무를 사용하였다. 실험결과 성토지지말뚝시스템의 효율은 일정한 말뚝간격비에서는 성토고가 증가할수록 비선형적으로 증가하여 이후 일정한 값에 수렴하는 경향을 나타내었다. 또한 성토고가 일정한 조건에서는 말뚝간격비가 증가할수록 효율의 크기는 감소하였다. 토목섬유를 보강한 경우, 무보강시와 비교하여 말뚝으로 전이되는 하중이 증가하는 것으로 나타났다. 이는 토목섬유의 보강이 연약지반의 거동을 억지하는데 효과가 있음을 나타내는 것이다. 결국 토목섬유보강 성토지지말뚝시스템에서의 하중전이 특성은 말뚝캡 설치간격, 성토고, 지반의 강도정수 및 토목섬유 강성 등에 복합적으로 영향을 받음을 알 수 있다.

• 한국철도학회논문집
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• 제12권2호
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• pp.276-284
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• 2009

최근 연약지반에서 급속시공과 엄격한 침하억제가 필요한 경우가 빈번해짐에 따라 성토지지 말뚝공법이 이에 대한 해결책으로 대두되고 있다. 특히 토목섬유로 보강한 성토지지 말뚝 공법의 경우 경제성 및 안정성 측면에서 효용성이 커서 전 세계적으로 활발히 적용되고 있다. 그러나 성토지지말뚝에서의 하중전달작용은 매우 복잡하여 아직까지 이에 대한 완전한 파악이 이루어지지 않은 상태이다. 특히 토목섬유의 보강 목적 및 효과에 대한 이해는 매우 부족한 상태로, 지반의 아칭효과에 의한 말뚝 지지효과를 보조하기 위한 수단으로서 토목섬유의 보강효과를 간주하고 있다. 본 논문에서는 3차원 유한요소해석을 이용한 변수연구를 통해 토목섬유의 보강효과를 구명하였다. 해석 결과의 분석을 통해 토목섬유의 보강 정도가 증가함에 따라 성토하중이 말뚝으로의 집중하는 작용이 지반의 아칭효과에서 토목섬유의 인장효과로 전이되는 현상을 발견하였다. 이는 토목섬유가 일방적으로 말뚝으로의 하중 전달 작용을 향상시킨다는 기존의 인식과는 상반된 결과이다 최종적으로는 기존 설계방법과 수치해석으로 산정된 설계변수의 비교를 통해 기존 설계방법의 문제점과 개선 방안을 제시하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.49-56
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• 2005

The negative skin friction on piles, which are installed in currently consolidating soft deposits, creates significant problems on the stability of pile foundations. This study investigated whether or not the pile foundation designs were appropriate in soft deposits with large amount of consolidation settlement. The final settlements of the grounds along the pile depth were estimated by the soil parameters obtained from the laboratory tests and by the field-measured settlement curves, if they were available. The displacement of the piles along the pile depth was estimated by both the load transfer method and the numerical method. Both methods gave similar locations of neutral points and magnitudes of the maximum axial forces. The movements of the ground and the piles were compared to calculate the down drag acting on piles. For the piles whose bearing capacities were less than the design loads including the down drag, slip layer coatings and/or incrementing of the penetration depth into the bearing stratum were proposed to improve the piles capacities.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.1695-1704
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• 2008

The problems associated with constructing high-speed concrete track embankments over soft compressible soil has lead to the development and/or extensive use of many of the ground improvement techniques used today. Drains, surcharge loading, and geosynthetic reinforcement, have all been used to solve the settlement and embankment stability issues associated with construction on soft soils. However, when time constraints are critical to the success of the project, owners have resorted to another innovative approach. Especially, the design criteria of residual settlement is limited as 30mm for concrete track embankment, it is very difficult to satisfy this standard using the former construction method. Pile net method consist of vertical columns that are designed to transfer the load of the embankment through the soft compressible soil layer to a firm foundation and one or more layers of geosynthetic reinforcement placed between the top of the columns and the bottom of the embankment. This paper will present the guidelines for the design of pile net method to supported embankments. These guidelines were developed based on a review of current design methodologies and a parametric study of design variables using numerical modeling.