• 한국ITS학회 논문지
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• 제10권1호
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• pp.42-48
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• 2011

본 논문에서는 GaN HEMT (Gallium Nitride High Electron Mobility Transistor) bare-chip을 이용하여 X-대역에서 수동로드 풀(Passive load-pull)을 수행하였다. 열로 인한 특성 변화가 최소화 된 동작 조건을 얻기 위해 드레인 바이어스 전압과 입력 RF 신호를 펄스로 인가하였다. 전자기장 시뮬레이션과 회로 시뮬레이션을 병행하여, 와이어 본딩 효과를 고려하여 드레인 경계면에서의 정확한 임피던스 정합 회로를 구현하였다. 임피던스를 변화시키기 위해 마이크로스트립 라인 스터브의 길이가 조절 가능한 회로를 설계하였다. 펄스 로드 풀 실험 결과 8.5 GHz에서 9.2 GHz 대역에서 최대 42.46 dBm의 출력 전력을 얻었으며, 58.7%의 드레인 효율 특성을 얻었다.

• 대한치과보철학회지
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• 제41권4호
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• pp.440-450
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• 2003

Statement of problem : The joints of removable partial denture alloys have failed frequently after routine usage. Purpose : The purpose of this study was to evaluate the mechanical properties of the laser welded Co-Cr alloys. Material and method : For this study 20 Co-Cr specimens were casted and 10 of them were seperated on the middle area and laser welded with Alpha laser welding machine(Siro Lasertec, Pforzheim, Germany). Rest of them which were as cast, were used as a control group. For the section of the experimental specimens, wire cutting machine was used to make a even gap of the all specimens. Laser welding was done with manufacturer's instrunction and tested each specimen by Instron Machine. Tensile strength, 0.2% yield strength and % elongations were recorded. Fractured surfaces were investigated with SEM. Results : The results were as follows : 1. The tensile strength of the laser welded group(617.7MPa) was about 75% of the as cast group(820.4MPa). It had stastically significant differences(p<0.05). 2. The % elongation of the experimental group was 6.6 which was lower than the control group(14.3). 3. Fracture of the experimental group occured in the welded surface and showed many voids. In contrast, the fracture surface of the control group was showed rough surfaces without any voids. Conclusion : The tensile strengths of the as-cast joints were higher than those for the laser welded joints, and the % elongation of the experimental group was lower than the control group. Porosity was found in laser-welded joints.

• 한국전자파학회논문지
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• 제17권2호
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• pp.134-138
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• 2006

S-대역 SPST MMIC 스위치의 격리도 특성을 두 서로 다른 RF 결합 방법 인 마이크로스트립(microstirp)과 접지 코플라나 웨이브가이드(GCPW) 선로로 구성하여 분석하였다. 스위치의 온-오프 격리도는 마이크로스트립 설계에 비하여 접지 코플라나 웨이브가이드 선로를 사용하는 경우 5.8 dB 개선되었고, 접지 코플라나 웨이브가이드 선로에 코플라나 와이어본드 결합을 적용하는 경우 6.9 dB 더 향상된 격리도 특성을 3.4 GHz의 주파수에서 얻을 수 있었다. 측정된 삽입 손실 및 IMD3는 $3.2{\sim}3.6\;GHz$ 대역에서 1.94 dB보다 작았으며, 64 dBc보다 큰 특성을 얻었다.

• Journal of Welding and Joining
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• 제33권4호
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• pp.37-43
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• 2015

Characteristics of dissimilar metal welds between STS 316L and carbon steel ASTM A516 Gr.70 made with GTAW have been evaluated in terms of microstructure, ferrite content, chemical analysis, hardness and corrosion resistance. Three heat inputs of 9.00, 11.25, 13.00kJ/cm were employed to make joints of dissimilar metals with ER309 wire. Based on microstructural examination, the amount of vermicular type of ${\delta}$-ferrite was increased with increasing heat input due to the increase of Creq/Nieq in the second layer of welds. Based on the EDX analysis of weld metals, Cr and Ni content in the 2nd layer increased while those content in the first layer of welds decreased with heat inputs. Cellular solidification mode in the 1st layer and dendritic solidification mode in the 2nd layer due to different cooling rates were prevailed, respectively. Heat affected zone which formed hard microstructure showed higher hardness than the weld metal. The salt spray test of dissimilar metals weld joints showed that the carbon steel surfaces only corroded. The weight loss rate due to corrosion increased up to 100hours but it decreased above 100 hours. There was little difference in the weight loss caused by corrosion regardless of heat inputs.

• 대한기계학회논문집A
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• 제38권3호
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• pp.289-294
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• 2014

일반적으로 산업용 로봇은 가반중량에 비해서 매우 큰 자중을 가지게 되며, 이로 인한 큰 중력토크를 보상하여야 하므로, 고사양의 모터/감속기를 사용하게 되어 제조단가가 높아진다. 이러한 머니퓰레이터의 자중 및 가반중량을 기계식 중력보상장치로 보상하게 된다면, 모터/감속기 사양을 크게 낮추어서 제조단가를 낮출 수 있다. 그러나 기존의 와이어 기반의 중력보상장치의 경우, 내구성 및 파손 등의 문제로 실용성이 낮았다. 본 연구에서는 이를 개선하고자 기어 및 롤러 기반의 내구성 높은 중력보상장치를 개발하고, 이를 사용하여 낮은 용량의 모터/감속기로도 가반하중 목표를 만족시킬 수 있는 중력보상 장치를 탑재한 머니퓰레이터를 개발하였다. 본 연구에서는 다양한 시뮬레이션 및 실험을 통하여 제안한 중력보상장치가 머니퓰레이터의 모든 자세에 대해서 중력에 대한 완전한 보상토크를 제공하였으며, 큰 가반하중에 대해서도 적절한 보상토크를 제공할 수 있음을 보였다.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2007년도 추계 종합학술대회 논문집
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• pp.126-129
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• 2007

최근 유무선 혼합망의 사용이 증가됨에 따라 무선망의 핸드오프, 경로 손실, 페이딩, 등과 같은 전송 오류의 원인을 개선하기 위한 연구가 전개되고 있다. 유선의 신뢰성을 보장하는 표준 TCP, SCTP를 무선망에 적용하는 것은 혼잡제어, 흐름제어의 메커니즘을 적용함으로써 데이터 전송의 효율을 저하시킨다. 본 연구는 무선망에서 SCTP를 적용하기 위해서 SCTP와 SNOOP을 혼합하는 것으로, 무선망에서 전송오류가 발생했을 때 BS의 동작과정을 개선한 것이다. BS(Basic Station : 기지국)는 전송오류 시 ZWP(Zero Window Probe)를 MN(Mobile Node:이동노드)에게 보내어 경로와 상태를 확인하고 RWND를 갱신하여 에러상태를 확인한다. 그리고 새로운 경로를 선택하고, FH(Fixed Host : 고정호스트)에게는 ZWA(Zero Window Advertisement)를 보내어 혼잡제어나, 흐름제어 메커니즘을 호출하는 것을 방지하고 대기상태로 기다리게 한다. 무선망의 연결이 안정된 후에 데이터 전송을 함으로써 데이터의 전송 효율을 약 10% 향상한다.

• International Journal of Safety
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• 제11권2호
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• pp.15-21
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• 2012

This paper is aimed to develop an electrical fire detection system (EFDS) which can analyze the possibility of electrical fire for overcurrent, leakage current and arc signals of panel board in traditional market shop. The EFDS adopted fuzzy logic and precursory data for overcurrent, leakage current and arc signals to evaluate the possibility of electrical fire. The signals are obtained directly from panel board in traditional market shops and fuzzy membership function is obtained from experiment, simulation, expert's advice. The overcurrent data is acquired by thermal data of normal and abnormal states (partial disconnection) on the insulated electrical wire, in accordance with the increase of the current signal, The leakage current data is obtained under various environments. The arc signal is acquisited by waveforms of instantaneous value in time domain and frequency band in frequency domain. The Fuzzy algorithm for DB of EFDS consists of fuzzification, inference engine by Mamdani's method and defuzzification by center of gravity method. In order to verify the performance and reliability of EFDS, it was applied to Jeon-Ju traditional market shops (90 shops) in Korea. Results show that EFDS in this paper is useful in alarming the fire case, which will prevent severe damage to human beings and properties, and reduce the electrical fires in a vulnerable area of electrical disaster.

• Journal of Korean Neurosurgical Society
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• 제48권1호
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• pp.37-45
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• 2010

Objective : Craniovertebral junction (CVJ) consists of the occipital bone that surrounds the foramen magnum, the atlas and the axis vertebrae. The mortality and morbidity is high for irreducible CVJ lesion with cervico-medullary compression. In a clinical retrospective study, the authors reviewed clinical and radiographic results of occipitocervical fusion using a various methods in 32 patients with CVJ instability. Methods : Thirty-two CVJ lesions (18 male and 14 female) were treated in our department for 12 years. Instability resulted from trauma (14 cases), rheumatoid arthritis (8 cases), assimilation of atlas (4 cases), tumor (2 cases), basilar invagination (2 cases) and miscellaneous (2 cases). Thirty-two patients were internally fixed with 7 anterior and posterior decompression with occipitocervical fusion, 15 posterior decompression and occipitocervical fusion with wire-rod, 5 C1-2 transarticular screw fixation, and 5 C1 lateral mass-C2 transpedicular screw. Outcome (mean follow-up period, 38 months) was based on clinical and radiographic review. The clinical outcome was assessed by Japanese Orthopedic Association (JOA) score. Results : Nine neurologically intact patients remained same after surgery. Among 23 patients with cervical myelopathy, clinical improvement was noted in 18 cases (78.3%). One patient died 2 months after the surgery because of pneumonia and sepsis. Fusion was achieved in 27 patients (93%) at last follow-up. No patient developed evidence of new, recurrent, or progressive instability. Conclusion : The authors conclude that early occipitocervical fusion to be recommended in case of reducible CVJ lesion and the appropriate decompression and occipitocervical fusion are recommended in case of irreducible craniovertebral junction lesion.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 D
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• pp.2696-2698
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• 2004

Iontophoresis를 이용한 경피전달용 약물 패치를 제작하기 위해 고분자의 종류, 전류크기, 시간에 따른 약물방출 결과를 발표한다. 고분자 Hydroxy Propyl Methyl Cellulose(HPMC), Hydroxy Propyl Cellulose(HPC), Hydroxy Ethyl Cellulose(HEC)에 각각 국소마취제-Lidocaine을 넣어 시료를 제작하였다. 약물 방출은 Drug Delivery Cell(DDC)위에 Ag/AgCl 전극 (anode), Pt wire 전극(cathode)을 각각 설치하여 전압인가에 따른 이온 유동으로부터 시간에 따른 전압/전류변화 및 약물농도를 고찰하였다. 전압 15V 인가 시 고분자 막과 전해질 사이에 흐르는 전류 1.0mA는 15분간 유지되지만, Ag/AgCl 전극의 산화작용으로 인해 전류는 서서히 감소하며 26분 후 거의 흐르지 않았다. 따라서 안정적인 전류로 유지되는 시간을 15분으로 최적화하였다. 고분자 중 HPMC 막을 사용하여 약물방출 실험을 한 경우 UV 분석결과 파장 262.26nm에서 최대 흡광도 0.238이었고, 가장 높은 약물농도가 나타났다. 이러한 HPMC의 약물방출 실험결과 비교적 높은 전류 1.0mA일 때 약물 방출량이 많았고, 동일한 전류 0.4mA를 장시간 흐르게 하였을 경우, 농도가 축적되므로 치료 가능한 안정적인 특성임을 확인하였다.

• 제어로봇시스템학회논문지
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• 제18권6호
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• pp.584-593
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• 2012

This paper introduces an AVP (Automated Valet Parking) system which applies an autonomous driving concept into the current PAS (Parking Assistant System). The present commercial PAS technology is limited into vehicle. It means vehicle only senses and controls by and for itself to assist the parking. Therefore, the present PAS is restricted to simple parking events. But AVP includes wider parking events and planning because it uses infra-sensor network as well as vehicle sensor. For the realization of AVP, the commercial steering system of a compact vehicle was modified into steer-by-wire structure and various sensors like LRF (Long Range Finder) and camera were installed in a parking area. And local & global server decides where and when the vehicle can go and park in the testing area after recognized the status of environment and vehicle from those sensors. GPS solution was used to validate the AVP performance. More various parking situations, vehicles and obstacles will be considered in the next research stages based on these results. And we expect this AVP solution with more intelligent vehicles can be applied in a big parking lot like a market, an amusement park, etc.