• 소성∙가공
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• 제14권2호
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• pp.153-159
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• 2005

Design modification of the stamping die for the upper member of a front end module carrier is carried out in order to improve the surface quality of the final product. The small inferiority induced by wrinkling near the wall of the upper member has been inspected after the draw-forming process. The finite element analysis is pursued with the whole geometry in order to consider the complicated shape. The simulation shows that the excess metal is developed by the irregular contact of the blank the tool and it remains after the final stroke. This paper proposes two guidelines for the modification. One is to add the draw-bead near the critical region in order to increase the draw-in force. The other is to modify the tool shape such as the forming shape at the wall in order to absorb the excess metal before the final stroke. Simulation results show that the proposed guidelines both guarantee the improved surface quality.

• Composites Research
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• 제24권3호
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• pp.12-16
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• 2011

경량복합소재의 고속인장시험을 수행하여 변형률속도에 따른 강도변화를 측정하고자 한다. 준 정적 시험인 경우 섬유강화 복합소재의 인장시험은 ASTM D3039에 따른 시편 형상이 사용되지만 고속 인장시험인 경우 표준화된 시편 형상에 대한 연구가 진행되어 있지 않다. 본 연구에서는 ASTM D638에 나타난 시편 형상을 기본으로 몇 가지 변형된 형태의 시편을 가지고 고속인장 시험을 수행하여 변형률 속도에 따른 경량복합소재의 강도 변화를 측정하였다. 낙하방식의 고속인장 시험기를 제작하여 변형률 속도 15/s, 100/s에서 시편의 형상에 따른 섬유강화 복합소재의 인장거동을 측정하였으며 시편의 폭이 6mm, 8mm, 10mm인 경우에 대하여 시험을 수행하였다. 측정 결과 시편의 폭이 8mm인 경우 섬유강화 복합소재의 강도를 정확하게 평가할 수 있는 것으로 나타났다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.252-255
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• 2004

Design modification of the stamping die for the upper member of a front end module carrier is carried out in order to improve the feeling qualify of the final product. The small inferiority induced by wrinkling near the wall of the FEM upper member has been inspected after the draw-forming process. The finite element simulation shows that the excess metal is developed by the irregular contact of the blank the tool and it remains after the final stroke. This paper proposes two guidelines for the modification: one is to add the draw-bead; and the other is to modify the tool shape such as the forming shape at the wall. Simulation results show that the proposed guidelines both guarantee the improved feeling quality.

• 한국산학기술학회논문지
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• 제16권1호
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• pp.8-14
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• 2015

지금까지 자동차 소재의 경량화 및 연소가스의 저감은 부품의 플라스틱화를 통하여 많은 진전이 있었다. 장섬유 보강 폴리프로필렌 소재가 적용된 프론트 엔드 모듈 캐리어는 플라스틱 구조부품 중에서 가장 성공적인 사례이다. 하지만, 장기 신뢰성 측면에서 볼 때, 자동차용 플라스틱 소재에 대한 피로거동 및 진동내구에 대한 더 많은 연구가 필요한 실정이다. 본 연구에서는 프론트 엔드 모듈 캐리어의 피로설계 및 해석의 기초가 되는 폴리프로필렌 장섬유 소재에 대한 내구성을 분석하였다. 피로수명과 응력진폭 또는 평균응력 간의 상관관계를 평가하기 위하여 다양한 응력비에서 피로실험을 수행하였다. 일정 응력진폭에서 응력비를 변화시킨 결과는 최대하중을 고정시킨 결과보다 피로수명의 변화가 응력비 증가에 따라 2~6% 크게 나타났다. 또한 주사전자 현미경을 통하여 장섬유 보강 폴리프로필렌 소재에 대한 피로균열의 발생, 전파의 파괴기구를 확인하였다.

• 한국자동차공학회논문집
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• 제12권6호
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• pp.103-110
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• 2004

The major trend in global automotive market is changing drastically in the way that a vehicle FECPS(Front End Cooling Pack System) is designed and manufactured as an assembly part. The system can encompass many functions, be assembled into a vehicle as a module, and reduce the production cost as well as time. The FECPS consists of an impact beam, an aluminum condenser and a radiator, a carrier and a cooling fan with a BLDC motor. In order to predict the performance of a FECPS accurately, it is essential to properly model the air flow field through various heat exchangers, such as a condenser or a radiator. In this study, the flow field of the system is measured by a PIV(Particle Image Velocimetry) system. The result is compared with that measured with multi-channel anemometer.

• JSTS:Journal of Semiconductor Technology and Science
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• 제11권4호
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• pp.295-301
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• 2011

A triple-band transceiver module for 2.3/2.5/3.5 GHz mobile WiMAX, IEEE 802.16e, applications is introduced. The suggested transceiver module consists of RFIC, reconfigurable/multi-resonance MIMO antenna, embedded PCB, mobile WiMAX base band, memory and channel selection front-end module. The RFIC is fabricated in $0.13{\mu}m$ RF CMOS process and has 3.5 dB noise figure(NF) of receiver and 1 dBm maximum power of transmitter with 68-pin QFN package, $8{\times}8\;mm^2$ area. The area reduction of transceiver module is achieved by using embedded PCB which decreases area by 9% of the area of transceiver module with normal PCB. The developed triple-band mobile WiMAX transceiver module is tested by performing radio conformance test(RCT) and measuring carrier to interference plus noise ratio (CINR) and received signal strength indication (RSSI) in each 2.3/2.5/3.5 GHz frequency.

• 한국전자파학회논문지
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• 제17권3호
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• pp.239-248
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• 2006

본 논문에서는 pHEMT(pseudo-morphic High Electron Mobility Transistor)로 구성된 저잡음 증폭기 MMIC(Monolithic Microwave Integrated Circuit)를 이용하여 극저온에서 동작하는 전파 망원경 수신기 전단부용 22 GH2 대역 저잡음 증폭기 모듈을 설계, 제작하였다. pHEMT MMIC 선정에는, 극저온에서의 동작이 입증된 pHEMT 공정을 사용하여 제작된 저잡음 증폭기 MMIC를 선택하였다. 선정된 2개의 MMIC는 박막(thin film) 세라믹 기판에 장착하여 모듈화 하였다. 모듈화 시 하우징(housing)과 캐리어(carrier) 사이의 간극을 제거하고 전파 흡수체를 사용하여 불필요한 구조에 의한 발진을 제거하였다. 또한 커넥터와 기판 사이의 부정합으로 나타나는 잡음 및 이득의 열화를 리본 조정을 통해 개선시켜 상온에서 최적의 성능을 가지도록 했다. 제작된 증폭기 모듈은 상온에서 $21.5{\sim}23.5GHz$ 대역 내 이득 $35dB{\pm}1dB$, 잡음지수 $2.37{\sim}2.57dB$를 보였다. 제작된 증폭기는 헬륨 냉각기를 이용하여 $15^{\circ}K$로 냉각 후 측정 결과, 대역 내에서 이득 35 dB 이상, 잡음온도 $28{\sim}37^{\circ}K$를 얻었다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.235-240
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• 2006

Ionospheric scintillation induces a rapid change in the amplitude and phase of radio wave signals. This is due to irregularities of electron density in the F-region of the ionosphere. It reduces the accuracy of both pseudorange and carrier phase measurements in GPS/satellite based Augmentation system (SBAS) receivers, and can cause loss of lock on the satellite signal. Scintillation is not as strong at mid-latitude regions such that positioning is not affected as much. Severe effects of scintillation occur mainly in a band approximately 20 degrees on either side of the magnetic equator and sometimes in the polar and auroral regions. Most scintillation occurs for a few hours after sunset during the peak years of the solar cycle. This paper focuses on estimation of the effects of ionospheric scintillation on GPS and SBAS signals using a software receiver. Software receivers have the advantage of flexibility over conventional receivers in examining performance. PC based receivers are especially effective in studying errors such as multipath and ionospheric scintillation. This is because it is possible to analyze IF signal data stored in host PC by the various processing algorithms. A L1 C/A software GPS receiver was developed consisting of a RF front-end module and a signal processing program on the PC. The RF front-end module consists of a down converter and a general purpose device for acquiring data. The signal processing program written in MATLAB implements signal acquisition, tracking, and pseudorange measurements. The receiver achieves standalone positioning with accuracy between 5 and 10 meters in 2drms. Typical phase locked loop (PLL) designs of GPS/SBAS receivers enable them to handle moderate amounts of scintillation. So the effects of ionospheric scintillation was estimated on the performance of GPS L1 C/A and SBAS receivers in terms of degradation of PLL accuracy considering the effect of various noise sources such as thermal noise jitter, ionospheric phase jitter and dynamic stress error.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2017년도 전력전자학술대회
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• pp.212-213
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• 2017

In this paper is presented a pre-charging sequence for single-phase cascaded neutal-point-clamped(NPC) converters for capacitors voltage balancing. capacitor imbalance problem in pre-charge sequence is caused in cascaded NPC converter by its topology. the DC link voltage at each NPC converter module can be balanced by the proposed switching method. the design and performance of the proposed sequence are verified by simulation and experimental results using prototype.